Introduction to Earth Science — Lecture Summaries for Fall 2017

 

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28 August – 1 September 2017 [Week 1]
Introduction to the Course

Please read appropriate sections of the textbook and lab manual prior to class (and lab) and take good notes. After class, reread the text and augment your notes, then see me if you are having difficulty; my office is in Bentley 332. Please do not fall behind or miss pieces of the puzzle.

Consider purchasing the textbook by Marshak and Rauber (2017) online at BookFinder4You or BooksPrice, or purchase it at the JSC Bookstore. The lab manual is not available online and may be purchased at the JSC Bookstore (yet there are only a few copies left).

See the class syllabus for required readings.

The first lecture will be held on Tuesday, 29 August 2017 in Bentley 206, starting at 1:00 p.m.

The first lab will be held on Wednesday, 30 August 2017 in Bentley 101, starting at 1:00 p.m. Please come to lab prepared to work with topographic maps.

A copy of the textbook and the lab manual are on reserve in the Willey Library.

 

Today's big idea: The higher cognitive domains of intellectual development allow us to apply the methods of science in order to explain how nature works. Scientists question everything and are always open to new observations, which in turn, allows us to improve our understanding of the fundamental laws of nature.



The Nature of Science

An overview of the course was presented during the first class meeting. Click here to learn about what geologists do and the types of careers that are available in the geosciences.

Put down your electronics; read a recent article by Mark Zuckerberg (founder of Facebook) entitled "The web has stolen my creativity".

The lecture began with a discussion of Bloom's Taxonomy of Educational Objectives (knowledge, comprehension, application, analysis, synthesis, and evaluation) and Dr. Andersen's modifications. The nature of science, and the distinction between observations, hypotheses, theories, and laws were introduced. Yogi Berra said: "You can observe a lot just by watching." Watch a seven-minute video about facts, hypotheses, theories and laws by Joe Hanson, Ph.D., or check out his website.

As scientists, we recognize patterns in nature when we observe phenomenon over and over again. Eventually, we generalize our experiences and summarize what we have learned. An assumption, subject to verification or proof, is a conjecture that accounts for a set of observations and can be used as a basis for further investigation. This is a hypothesis. It is, in fact, a proposal. It is a tentative explanation for an observation, phenomenon, or scientific problem that can be tested by further investigation. We consider these types of ideas to be hypotheses.  Scientific hypotheses must be posed in a form that allows them to be rejected.

Theories, on the other hand, are well tested and widely accepted hypothesis. Theories model a restricted part of the universe. They are models with a set of rules. A good theory has two properties: 1) they describe a large class of observations with few arbitrary elements, and 2) they make definite predictions about the results of future observations.

Read the Dec 2010 paper about the relationship between brain tumors and cell phone use (published in the Journal of Computer Assisted Tomography, volume 34). Take a look at the SAR rating for your cell phone, and if it is high, then try and keep it at least one inch away from your head (or get a safer phone). See the SAR site of the Federal Communications Commission.

For all health and safety issues it is often wise to apply the Precautionary Principle. The Wingspread Conference defined the Precautionary Principle as follows: "When an activity raises threats of harm to human health or the environment, precautionary measures should be taken even if some cause and effect relationships are not fully established scientifically".

 

Galaxies
The sun is but one star in the Milky Way Galaxy; it is an average aged star that holds no special position in our galaxy nor is it distinct from other middle-aged stars. The Milky Way Galaxy is one of many spiral barred galaxies that are observed in the universe. There are also irregular, elliptical, and rare ringed galaxies. Stars in the Big Dipper are about 75 light years from Earth (that means that when we look at the Big Dipper today, we see the events that occurred 75 years ago).

The nearest galaxy is the Andromeda Galaxy that is 2.5 million light years away from Earth. 

The nearest star is Proxima Centauri (part of star cluster Alpha Centauri) that is 4.22 light years away from Earth. Proxima b is an Earth-like planet orbiting this star.

The electromagnetic spectrum (EM) incorporates the full range of frequencies from the very long radio waves to the very short gamma rays; visible light is also part of the EM spectrum. All waves in the EM move at the speed of light. Light travels at 299,792,458 meters per second (that corresponds to 670,616,629 miles per hour). The distance that light travels in one year, about 5.9 trillion miles, is regarded as a light year.

Some videos and images of relevance:

Several telescopes are being built to allow us to see further and more clearly:






Lecture

PowerPoint slides: Science

PowerPoint slides: Galaxies

 

Laboratory

PowerPoint slides: Topography

PowerPoint slides: Latitude and longitude

Lab: Topography





Lab: Topographic Maps

Topographic maps depict the landforms by use of contour lines. Contour lines are lines of equal elevation; the contour interval specifies the difference in elevation between two adjacent contour lines. Contour lines specify the elevation above mean high tide. Index contour lines are bold and labeled (every fifth contour line on the map). Features on topographic maps are represented by a wide variety of symbols.

Bar and ratio scales are used to convey distances – these scales are the horizontal scales of the map. Ratio scales are unitless (or have the same units on both sides) and are always expressed as 1:X (where X is any number). A map scale of 1:24,000 means that one unit on the map (any unit) represents 24,000 of those same units on the ground.

Topozone.com supplies topographic maps, for free, for most of the USA; or visit the USGS Store for topographic maps (or here for the Johnson Quad); also see historic topographic maps of Vermont. See An Introduction To Topographic Maps Tutorial from the Geospatial Training And Analysis Cooperative, Idaho State University. CalTopo.com provides a fantastic set of maps for free.

 

Lab Assignment (due 6 September 2017): Map scale and north

Use the map supplied in lab and complete the following:

  1. Determine the dimensions of the Summit Bookstore.
  2. Calculate the ratio scale for the map (based on the dimensions of the Summit Bookstore).
  3. Draw a bar scale of the correct length that is 50 m long and has 10-m divisions.
  4. Draw a true north arrow and a magnetic north arrow properly oriented on the map (in the correct box) and labeled as true north and magnetic north.
  5. Show all work (including calculations for your pace factor) on back of paper and place all results in the proper boxes on the front of the map.
  6. Be sure that units are associated with all numbers (except, of course, the ratio, scale which is unitless).
  7. Print extremely legibly.

 



4 – 8 September 2017 [Week 2]

 

Today's big idea: Redshifted spectra indicate the universe is expanding. The expansion rates are consistent with our understanding of how the universe evolved since the beginning of time, the time of the Big Bang. The results of experiments using the Large Hadron Collider have provided more evidence in support of the Standard Model. This model describes the fundamental forces, fundamental particles, and laws of nature that describe our understanding of the evolution of the universe.


Formation of the Universe

The galaxies seem to be surrounded by dark matter and the center of many galaxies are presumed to be black holes. The universe is composed of 4.6% ordinary (normal) matter, 24.0% dark matter, and 71.4% dark energy (the cosmic pie). WIMPs and MACHOs may be the fundamental particles that provides the mass not observed, but inferred, in the universe. WIMPs (about 100 GeV) have the right thermal relic abundance to account for dark matter. Dark matter annihilates into quarks.

Dark energy may be the force that beats out gravity and is causing the universe to expand at an ever-increasing pace. Dark matter does not emit or reflect light, so it can't be seen. We infer the existence of dark matter through its gravitational effect on normal matter. It may be comprised of various types of exotic particles with names such as neutralinos, axions and gravitinos. Dark matter may account for the formation of the first stars (normal matter). Recent reports suggest that the atoms that make up stars, planets, air, and life account for only a small fraction of what must exist. Either our understanding of gravity is wrong, or an additional source of gravity is required to stop galaxies from flying apart. It is theorized that dark matter could be this additional source of gravity. Watch Professor Lisa Randall describe dark matter.

A Big Bang theory attempts to explain the early evolution of the universe that we believe began about 13.82 Ga; 1 Ga = billion years.  Click here for a series of essays on cosmological evolution. In March 2014, Prof John Kovac of the Harvard-Smithsonian Center for Astrophysics, new evidence to support a Big Bang Theory.

Read Roger Penrose's brief description of his Conformal Cyclic Cosmology theory, or listen to Lawrence Krauss speak about 'A Universe From Nothing'.

The European Center for Nuclear Research (CERN) attempted to start experiments on 10 Sep 2008 using the Large Hadron Collider (LHC). Watch a video introduction of the LHC. The $10,000,000,000 LHC at CERN is back online after a 14-month repair to some of the magnets. Click here for a rap song regarding the LHC. The LHC will model situations associated with the Big Bang, dark matter, dark energy, and the evolution of galaxies. Click here for a general introduction to CERN and the LHC (text and videos). Fantastic pictures of the LHC are published by the Boston Globe.

Listen to Brian Greene discuss superstring theory (eleven-dimensional space) or Patricia Burchat discuss dark matter.

Click here if you are interested in learning more about Dr. Peter Higgs and Higgs Boson. Other exotic hadrons have been identified by the LHC.

If you have questions about astronomy, then Ask An Astronomer (or read answers to other questions already posted on that site). Learn about the first observed neutron star collsion.

If you want to get involved in a distributed computing research project, view many of the opportunities in a site maintained by Kirk Pearson, or join the Galaxy Zoo and become a citizen scientist astronomer.

Stephen Hawking is a pre-eminent astrophysicist at Gonville and Caius College at the University of Cambridge. He is the former Lucasian professor of theoretical physics and mathematics. Learn more about Stephen Hawking by accessing some of the following links:

 

Redshift and the Evolution of the Universe

Red-shifted spectra indicate the rates at which stars (and galaxies) are moving away from other stars (and galaxies). The farther the spectral lines are shifted into the red (i.e. longer wavelengths), the faster the stars are receding. Distances to stars are measured by stellar parallax.

Observations of the Solar System

The solar system comprises the sun, planets, asteroids, moons (and other rocks and gasses that encircle some planets) and some comets. High Resolution Imaging Science Experiment (HiRISE) camera mounted on NASA's Mars Reconnaissance Orbiter has produced amazing photographs of Mars.

See a video of the Space Shuttle conducting a backflip and other images of shuttle launch preparation (a 3 Mb PowerPoint file). The Space Shuttle will be retired and DIRECT or SpaceX may be the replacement space vehicle. Have you ever wondered how astronauts on the International Space Station (ISS) go to the bathroom without a gravity assist (this link too)? View a video about life inside the ISS. The first espresso machine was just delivered to the ISS.

In September 2002, a large object in the Kupier Belt was identified and given the name Quaoar. Some considered this object to be the tenth planet in the solar system. In March 2004, another planet-like body was discovered at the fringes of our solar system. The object is three times farther away from Earth than Pluto, making it the most distant known object in the solar system. At its most distant, Sedna is 130 billion kilometers (84 billion miles) from the Sun and larger than Quaoar. Until Sedna was detected, Quaoar was the largest known body beyond Pluto. Vesta and Ceres are the most massive objects in the asteroid belt. In June 2012, Vesta was reclassified as a protoplanet – prior to that it was classified as an asteroid.

On 24 August 2006, the International Astronomical Union redefined the term planet – our solar system now has only eight planets; the trans-neptunian bodies are not planets – Pluto is no longer regarded as a planet, but as a dwarf planet. In July 2015 the New Horizons spacecraft should be passing by the Pluto system (that includes six moons); the craft will have travelled about 3 billion miles from Earth – it takes 4 hours and 26 minutes for electromagnetic waves to travel that distance!

Some of the consistent observations of the solar system include:





Lecture
PowerPoint slides: Redshift

PowerPoint slides: Solar system
Laboratory
Lab: Topography

 



Lab: Coordinate Systems

Coordinate systems (latitude & longitude or the Universal Trans Mercator system) can be used to locate a place on Earth. Latitude (0 - 90º) measures the angular distance (N or S) from the equator; longitude (0 - 180º) measures the angular distance (E or W) from the Prime Meridian. One degree (º) of arc is equivalent to 60 minutes (') of arc; 1 minute of arc is equivalent to 60 seconds (") of arc. Furthermore, 1º of latitude (not longitude) is equivalent to 111 km of distance (60 nautical miles or 69 statute miles).

The Universal Trans Mercator system is based on meters (not degrees). The seven digit values report northings an eastings. Each unit is one meter in length. The UTM system is designed to be used for latitudes between 80°S and 84°N; it does not include the polar regions. The origin of each zone is the equator and its central meridian. In the Southern hemisphere the 0 value is referenced to the latitude which is 10,000,000 meters south of the equator. The value given to the central meridian of each zone is a false easting of 500,000.

Vertical exaggeration (VE) is a number that represents how many times the vertical scale is amplified (larger) with respect to the horizontal scale. The horizontal scale is fixed for any given map, it does not change. A cross section with no vertical exaggeration has a horizontal scale (map scale) equal to the vertical scale (of the cross section). Use the horizontal scale as the basis for determining the vertical scale when constructing a topographic cross section. Scaling along the vertical axis of the cross-section determines the vertical exaggeration.

 

Lab Assignment (due 13 September 2017): Topographic maps, scales, and cross sections

  1. Submit the topographic map created in lab.
  2. Draw two cross-sections, one without vertical exaggeration (VE) and a second cross-section with a VE equal to 3. Be sure to clearly label all cross sections (specify the vertical exaggeration for each cross section, put the units on the vertical axis, and compass directions of the traverse).
  3. Calculate the ratio scale for your map. Be sure to clearly write out the equations and show all of your work.

Please submit the map drawn in class and the cross-section handout. Answer Question 3 on the back of the cross-section handout, be sure to show all mathematical work, and write legibly. You do not have to type up this assignment because there are few words with a little bit of math.

 



11 – 15 September 2017 [Week 3]

 

Today's big idea: Planets form by accretion of chemically similar particles created when a new star forms. The regular change in chemistry of the planets, with increasing distance from the sun, is related to temperature. The gas giant planets are found farther from the sun where the lower temperature allows gasses to condense (gasses burn off nearer to the sun). As chemically similar particles accrete to form a planet, the temperature of the early forming planet heats up to the melting temperature of iron and the result is the iron catastrophe and initiation of convection that accounts for a layered planet.



Formation of Earth

The NASA Mars Science Laboratory with the Curiosity rover is on Mars. Curiosity's electrical power will be supplied by a U.S. Department of Energy radioisotope power generator that produces electricity from the heat of radioactive decay of 238-Plutonium. Watch an animation of Curiosity's landing.

There are planets that orbit other stars. Extrasolar planets exist – the sun is not the only star that has orbiting planets; see the Extrasolar Planets Encyclopaedia. Astronomers recently identified a fifth planet in a solar system only 41 light years from Earth. We have now identified about 3668 extrasolar planets. In November 2008, NASA's Hubble Space Telescope took the first visible-light snapshot of a planet circling a star; the star is only 25 light years away!

There are about 1803 potentially hazardous asteroids (PHA) and comets that are continuously monitored. A PHA has a minimum orbit intersection distance of 0.05 astronomical units (AU); one AU is the distance between the Earth and the sun (149,000,000 km). See SpaceWeather.com for more information. Click here to view an animation of known objects close to Earth; click here to see more animations and associated descriptions. Look at the catalogue of Earth Impact Structures (190 sites have been identified) and look at terrestrial impact craters. Take a look at the Meteorite Catalogue Database from the Natural History Museum or calculate the effects of bolide impacts. The American Meteor Society observes, monitors, collects data on, studies, and reports all things related to meteors. Space junk (debris from older satellites) poses a major problem for satellites in orbit around Earth.

On 14 Feb 2012 a record setting asteroid, about 50 meters in diameter, came within 0.09 lunar distances of Earth. On the same day a 15-meter diameter meteorite burnt up in Earth's atmosphere (25 km) and blew out windows over a distance of several hundred miles. See numerous videos of this event here or here. Meteors of this size hit Earth, on average, every 1200 years, yet the Tunguska Event in 1908 was much larger. Monitor the space weather here.

NEOshield is a project to assess how we can protect Earth from Near Earth Objects (NEO) through use of kinetic impactors, gravity tractors, or blast deflection. There are over 10,000 NEOs and more are found each month. NEOs, in general, have orbits around 1.0 AU. A re-analysis of historical observations suggest Earth narrowly avoided an extinction event just over a hundred years ago. The Hayabusa spacecraft just returned samples from asteroid Itowaka. Keep an eye out for Apophis – a very close approach to Earth on Friday, 13 April 2029 at 30,000 km; it may hit on 13 April 2036! Deep Space Industries hopes to mine asteroids and intends on sending prospecting satellites in 2015 (with larger spacecraft embarking on round trips later that year to collect and return material from asteroids). The Asteroid Deflection Research Center, at Iowa State University, has been studying a variety of ways to address the potential problems of asteroid impacts.

Comet ISON had a fantastic showing in November 2013. Europe's Rosetta spacecraft entered orbit around comet 67P/Churyumov-Gerasimenko and crash landed a probe on its surface in November 2014; click here for its travel path. Click here and here to read more about a comet that was more than eight times larger than Halley's Comet and just missed Earth.

Look at the Earth and moon viewer, or look at the current position of the sun, Earth, and Luna (Earth's moon).  Click here to plan for viewing the next meteor shower, then use NASA's Fluxtimator to find the best time to view the most meteors.

Voyager 1 was launched in 1977. In late 2012 it reached the edge of the solar system and is now flying in interstellar space. This is the first and only craft that has travelled such a distance. It takes light about 17 hours to travel such a distance.

The solar system formed by gravitational compression of a spinning cloud of interstellar dust particles. The cloud imploded and material was ejected from this event. The composition of the dust particles ejected from this event followed the chemical condensation sequence (i.e. those materials with lower melting points condensed at greater distances from the sun). Read more about the geochemistry of Titan, one of Jupiter's moons.

Protoplanets (young planets) formed by the accretion of nearby, homogeneous, material ejected by the newly formed star. Protoplanets of the asteroid belt, however, did not coalesce to become a planet. Protoplanets formed through the process of homogeneous cold accretion, that is, all the materials in a specific distance from the newly formed sun has the same composition (i.e. homogeneous). Accretion was accompanied by bombardment, gravitational compression, and radiogenic decay – all of which resulted in a temperature increase of the early Earth. After 1 Ga (billion years) of heating associated with accretion, early Earth heated to the melting point of iron, which resulted in the iron catastrophe. The iron catastrophe is represented by denser material sinking toward the center and lighter material moving toward the surface of Earth. This initiated convection (that now drives plate motion) and differentiation (layering) of Earth.

Convection is the driving force behind plate movements and is thus responsible for most of the plate movements, earthquakes, and volcanoes that occur on Earth.

The common minerals (silicates) are made of the common elements in Earth's crust (O, Si, Al, Fe, Ca, Na, K, and Mg). These elements are common in the crust because of the differentiation (layering due to density differences) associated with the iron catastrophe.

Earth's interior can be modeled through seismic tomography. The deepest hole drilled was on Russia's Kola Peninsula. It took over 20 years to drill to a depth of 12,262 meters. A few years ago the deep sea drilling vessel, Chikyu, was commissioned to conduct deep drilling. The ship’s drill stem is 10,000 meters long! It won’t beat the record depth of over 12,000 meters, but it can drill more quickly and recover cores.

Earth's early atmosphere and oceans were a result of the degassing of the planet. Over time the composition of the atmosphere changed (more oxygen-rich), thus allowing life to move from the oceans onto land and evolve to present-day conditions. Early life on this planet may have been seeded by comet impacts. The simple organic compound methane, and water, were found in the atmosphere of a hot (900ºC), Jupiter-sized planet orbiting a star (HD 189733b) some 63 light years away from Earth. This is the first time we have been able to detect an organic molecule on another planet!

 

 

Today's big idea: The mass of an atom, and ultimately the density of all materials, is controlled by the total number of protons and neutrons in the nucleus of an atom. We name the atom by counting the number of protons, and we name the isotope of an atom by adding the number of neutrons to the number of protons. The size of the atom, and bonding atoms together, is primarily controlled by the electron cloud.

 

Atoms

There are hundreds of subatomic particles; all subatomic particles are made of quarks. For simplicity, we are interested in only three subatomic particles: protons, neutrons, and electrons:

The atomic mass of an element represents a weighted average of all of the isotopes of that type of atom. For example, the average atomic mass of carbon, C, is 12.011 amu. Some isotopes of carbon have 5, 6, 7, or 8 neutrons (11C, 12C, 13C, or 14C respectively). Most isotopes of carbon have 6 neutrons and therefore the average atomic mass of carbon is about 12 amu (6 neutrons + 6 protons). See the table of nuclides produced by Brookhaven National Laboratories. Isotopes are atoms of the same type (same atomic number, i.e. same number of protons) but have varying atomic mass (i.e. varying numbers of neutrons). Some isotopes are stable and others are unstable (radioactive). There is no magic formula for determining which isotope of an atom is unstable; the stability of an isotope is governed by the weak nuclear force. Read more about isotopes from the US Geological Survey. Hydrogen has numerous isotopes: 1H (hydrogen), 2H (deuterium), and 3H (tritium); read about the sources and health effects of tritium. There are shortages of 99Mb (molybdenum) which are causing delays for certain medical tests (such as heart and kidney function tests and bone scans, including those looking for tumors).

A mol is equivalent to 6.022 x 1023 of similar atoms (known as Avogadro's Number). A mol of atoms is equal in weight (in grams) to the atomic mass of that element. In other words, it takes 6.022 x 1023 atoms to account for the mass of one mol of atoms of a specific isotope. The atomic mass of an atom depends on the density of the atom, and the density of the atom depends on the number of neutrons and protons in the nucleus of the atom. Read more about the structure of matter at the Nobel e-museum. Atomic scale images have been created by IBM, or listen to a song about the elements, or a song about quarks.

Neutrons and protons are found in the nucleus of an atom and define the atomic mass of that atom. Electrons are found around the nucleus in various orbitals, also known as energy levels (as described by the Schrödinger wave equation). Electrons fill the orbitals according to the Octet Rule and the Bohr Theory, which states that a maximum of eight electrons can occur in any orbital (except the first, which can hold only two electrons). The Bohr Theory is only somewhat applicable to atoms of low atomic number; it is a good model to demonstrate valence shell electrons and bonding. The number of electrons in the outermost orbital are the valence shell electrons. Valence shell electrons control bonding. The columns on the periodic table of the elements indicate the number of valence shell electrons.

Atoms bond with other atoms to make minerals. Atoms seek to have a full valence shell of electrons (the Octet Rule) and follow Pauling's Rules. Atoms fill their valence shells by transferring (ionic bonds), sharing (covalent bonds), or borrowing (metallic bonds) electrons from other atoms.

Minerals

Minerals are uniquely defined by their chemical composition and crystal structure. This in turn governs mineral properties and mineral symmetry (for example, mirror planes or rotation axes). The regular, repetitive, crystal structure forms when atoms bond according the Octet Rule and Pauling's Rules. The repeating unit cell, the motif, contains all of the atoms (in the correct proportions) that are required to define the chemical formula of that mineral. Click here to see Snowflake Bentley's hexagonal snow crystals, or click here to make virtual snowflakes.

Mineral classes are defined by their anion molecule. A few examples include: the silicates (SiO4-4), carbonates (CO3-2), and chlorides (Cl-1). Click here to see one of the largest mineral databases on the Internet, click here for another database, or read about some of the largest minerals in the world that are found at the Naica Cave system.

Atoms bond together to make minerals; minerals come together to make rocks. Rocks look different from each other because they are made of different minerals and the minerals have different appearances (textures) in different rocks. The texture of a rock depends on how it was formed. The common igneous rocks (Bowen's Reaction Series) comprise the common minerals (silicates) that are made of the common elements (O, Si, Al, Fe, Ca, Na, K, and Mg) in Earth's crust (as a result of the iron catastrophe).

See the website for the Vermont Geological Society to view common rocks of the state of Vermont. 

Homework (due 20 September 2017): The unit cell

Outline the unit cell and write out the chemical formula for the geometric pattern distributed in class. Please note that if half of one atom is outside the unit cell, then the other half should be found on the other side of the unit cell and there will always be a whole number of atoms (no halves or quarters of atoms). The unit cell will be the smallest geometric shape whereby all lattice points have similar environments. Draw about ten adjacent unit cells on the handout.




Lecture
PowerPoint slides: Atoms and minerals

Laboratory
Lab: Minerals




 

Lab: Minerals

In lab we explored the properties minerals and distinguished elements from minerals, and minerals from rocks. Atoms are defined by the number of protons in the nucleus, minerals are defined by the types atoms and structural arrangement of the atoms in the mineral, whereas, rocks are defined by the types of minerals and the textural arrangement of the minerals in the rock.

 

Lab Assignment (due 20 September 2017): Watershed

  • Submit the topographic map handout and answer all questions on that sheet.
  • Clearly show the mathematics for Question 2 on the back of the handout.
  • Use a sharp pencil (or very fine point pen) to draw precise lines that delineate the Basin Brook watershed.

 



18 – 22 September 2017 [Week 4]

 

Today's big idea: The weak nuclear force controls the mechanism and rate of decay of unstable isotopes. Unstable isotopes can be used for dating geological events, medical technology, nuclear energy, and nuclear weapons.

 

Time

The US Naval Observatory is the official time keeper for the United States; also see the NIST Physics Laboratory for more information. Click here for the official US time. Click here for a copy of a geological time scale. for a geological time scale. Or see an interesting page about dates (and links to other calendar pages). Click here for a discussion of calendars or here for the justification for a lot of time-related events.

Easter can never occur before March 22 or later than April 25. The day that Easter is celebrated is governed by relative positions of Earth, sun and moon; click here for more information.

A positive leap second was introduced on midnight 30 June 2015. Leap seconds can be either positive or negative depending on the Earth's rotation. Since the first leap second in 1972, all leap seconds have been positive and there were 26 leap seconds in the 43 years to June 2015. This pattern reflects the general slowing trend of the Earth due to tidal braking.

In 2005, President Bush signed into law a new energy policy bill that extended Daylight Saving Time by four weeks (beginning in 2007):

The Mayan calendar does not predict the end of the world, it only marks the end of a calendar era. Read more about it from the BBC, Reuters, and NASA.

Humans have had such an Effect on Earth's systems that a new Era has been suggested: Anthropocene Era.

 

Unstable Isotopes and Absolute Dating

The main thrust of today's lecture dealt with absolute dating. Nuclear chemistry allows us to date geological events by use of unstable isotopes. Isotopes can be identified by use of a mass spectrometer. Unstable isotopes generate radiation as the nucleus undergoes spontaneous decay. The weak nuclear force controls the rate and mechanism of the decay of the nucleus.

Common decay mechanisms include:

Half-life is the average amount of time required for one half of the original number of radioactive atoms (parent atoms) to decay to child (daughter) products. Unstable isotopes are used for absolute dating. Each isotope has a defined half life. After five half lives, only 1/32 of the parent isotope remains; this small amount is difficult to measure accurately so we choose an isotope that has a half life appropriate to the age of the feature of interest (for example, depositional age, age of crystallization, or age of metamorphism).

 

Radiation

The Vermont Department of Health can also test your water for a large number of contaminants. A Gross Alpha test (section 4 RA) costs $45. Click for forms and ordering information; get the order form for all water tests (and costs); read the supplement associated with the order form.

Radon is an unstable isotope that occurs as a gas and forms from the decay of radium. Radon gas is a problem in many dwellings because radium may often be substituted for other elements that have two valence electrons. According to a report by the National Academy of Sciences, radon is estimated to cause between 15,000 and 22,000 lung cancer deaths per year. It is the second leading cause of lung cancer after smoking. Please read more about Radon found at the Vermont Health & The Environment website.

Read about a Russian spy who exposed Russian President Putin's ring of corruption and was subsequently poisoned by radioactive 210Po while in London. Or learn more about the "Radium Girls" who are still glowing in their coffins.

 

Nuclear Energy

The isotope of choice for nuclear power is 235U because it is easily fissile, yet 235U represents only 0.7204% of all uranium; 99.2742% of all uranium is 238U. Enriched uranium is represented by a concentration of 3-5% of 235U. Enriched uranium is used in nuclear power plants where the uranium splits (nuclear fission), gives off heat, and numerous daughter products that have long and varied decay chains. The decay chain for 238U is also long and varied that it spawns numerous unstable isotopes that give off radiation in perpetuity. The heat given off when splitting 235U is used to boil water, that turns to steam, that turns a turbine, that spins a generator, that makes electricity. Nuclear power is an expensive way to boil water.

Highly enriched uranium is represented by a concentration of 90-95% of 235U and is used in nuclear weapons.

By concentrating 235U, that is enriching the sample with respect to 235U, what is left behind is referred to as depleted uranium (depleted with respect to 235U). Depleted uranium is used in armor-piercing bullets.

On 9 Feb 2011 the first license for nuclear power plant construction in the United States was issued since 1978! The AP1000 reactors built by Westinghouse Electric and will be constructed at the Vogtle nuclear reactor site, east of Atlanta, at the Savannah River. They are expected to cost roughly $14 billion and may receive a more than $8 billion loan guarantee from the federal government. What's interesting is that the Chairman of the Nuclear Regulatory Commission voted against the construction of these reactors. It sounds like a really expensive way to boil water. Learn about the failed Yucca Mountain Project here.

On 17 February 2015: Thousands of cracks were found in Belgian nuclear reactors. In a reaction to this, the Director General of the Belgian nuclear regulator, The Federal Agency for Nuclear Control, stated that, "This may be a global problem for the entire nuclear industry. The solution is to implement worldwide, accurate inspections of all 430 nuclear power plants.” Read more by clicking here.

 




Lecture

PowerPoint slides: Isotopes

PowerPoints slides: Uniformitarianism

Laboratory

Lab: Relative dating






 

Lab: Geological Time

Lab Assignment (due 27 Sep 2017): Relative Dating

Today we discussed geological time, relative dating, Steno's Principles, cross-cutting relationships (folding, tilting, metamorphism, faults, intrusions), and unconformities (erosional surfaces). View animations of relative dating and unconformities or faulting. Complete Figure 11 (p. 91 from the lab manual). Use the geological processes discussed in lab (deposition; erosion or unconformity; intrusion: dike, sill, or batholith; lava flow; fault: normal or reverse; and deformation: folding or tilting), the name of the rock unit, and the identity (a letter) for each event. Be sure to type the response and put the oldest event on the bottom of the list.





Field Trip

Three points of extra-credit.

The field trip will be held on Sunday, 23 September 2017. We will meet at 8:30 a.m. (in the Bentley Parking Lot) and return by 5:00 p.m.; or you can meet us at 9:30 in South Burlington at Dunkin Donuts (click here for a map). We will visit Redstone Quarry, Salmon Hole, Lessor's Quarry, and The Beam (located in South Burlington, Burlington, and South Hero, respectively). Please wear appropriate clothing and bring lunch (and water).

Click here for the weather forecast in Johnson or here for Burlington.


Definition of the UV Index

 

 



25 – 29 September 2017 [Week 5]
Gravity and Isostacy

Gravity is a force of attraction; this force is always perpendicular to Earth’s surface and measured in gals. Earth’s gravitational attraction = 980.665 gals = 9.80655 m/s2 = 980.665 cm/s2. The pull of gravity varies on Earth because of: centrifugal force (Earth spins at 1669 km/h at the equator), latitude (polar radius: 6357 km, equatorial radius: 6378 km), near surface mass, and topography.

Launched on 17 March 2009, ESA's Gravity field and steady-state Ocean Circulation Explorer (GOCE) was developed to measure Earth's gravity field. GOCE will map global variations in the gravity field with extreme detail and accuracy.

After corrections for centrifugal force, latitude, near surface mass, and topography are made, and a gravity anomaly still exists, it could be related to crustal areas seeking isostatic balance. Isostacy describes a mechanism where areas of Earth’s crust rise or subside until the mass of the topography is buoyantly supported (compensated) by the thickness of the crust that "floats" on denser mantle. Negative anomalies may occur over regions where the crust has not rebounded from the retreat of ice sheets, mountain roots, sedimentary basins, rift basins, subduction zones, mid-ocean ridges, or over salt domes. Positive may anomalies occur over ore bodies.

Airy Hypothesis: an equilibrium of crustal blocks of the same density but of different size; thus the topographically higher mountains would be of the same density as other crustal bocks (but would have greater mass and deeper roots).

Pratt Hypothesis: an equilibrium of crustal blocks of varying density; the topographically higher mountains would be less dense than the topographically lower units and the depth of the crustal material would be everywhere the same.

 

Geothermal Gradient

The geothermal gradient measures the temperature change with depth below Earth's surface. The average geothermal gradient (GG) is approximately 30ºC/km. At divergent plate boundaries the GG is higher than the average, whereas at convergent plate boundaries the GG is lower than the average. The rocks that form along plate boundaries reflect the geothermal gradient and the composition of the source material. Low geothermal gradients are commonly associated with subduction zones; the rocks that form under these conditions reflect the conditions of low temperature, high pressure, and mafic (basaltic) composition.

Magnetism

Polar lights: The northern lights (Aurora Borealis) have the same origins as the southern lights (Aurora Australis). The solar winds, associated with solar flares and coronal mass ejections, produce solar protons that interact with Earth's magnetic field. This interaction produces bands of light that are oriented parallel to the lines of magnetic force (which are directed toward the north and south magnetic poles of Earth). The colors of the polar lights are related to atmospheric chemistry: nitrogen produces red bands of light, whereas oxygen produces green and white bands of light.

Earth's magnetic field represents yet another aspect of electromagnetism. The electromagnetic spectrum is continuous with frequencies ranging from zero to about 1023 Hz. The magnetic field is created by a flow of electrons because a charged particle moving with uniform motion creates a magnetic field around itself.

The source of Earth's magnetic field results from the interaction of the inner core and the partially ionized outer core. Convection in the outer core distorts the magnetic field and causes it to wander.

Navigation: The needle on a compass points toward magnetic north. Magnetic north is not always coincident with true north (the geographic north pole). The angular difference between true north and magnetic north is called declination. The declination must be known in order for a compass to work properly. Magnetic north moves about 10 to 40 meters per day (27 to 109 km per year), and therefore the declination is always changing, this is known as secular variation. Furthermore, each location on Earth has a specific declination. See the US Geological Survey's National Geomagnetism Program for more information. Compute the values of the magnetic field in your area through the NOAA site. The declination in Johnson, VT, on 28 September 2017 is 14° 36' W changing by 0° 4' E per year.

Paleolatitude: The lines of magnetic force are perpendicular to Earth's surface at the polar regions and parallel to Earth's surface in the equatorial regions – this is only true when the declination is zero, otherwise we must consider the north magnetic pole and the magnetic equator. If the movement of the north magnetic pole is averaged over 10,000 years then it coincides with the geographic North Pole. When molten material cools beneath the Curie point (about 450ºC), magnetic domains form, and the ambient magnetic field is locked into the rock; this is known as thermal remnant magnetism (TRM). Iron-rich cements associated with sedimentary rocks also tend to align with the ambient magnetic field during lithification; this is known as depositional remnant magnetism (DRM). TRM and DRM are used to determine the latitude where the rocks formed.

Sea-floor spreading: Reversals of Earth's magnetic field are recorded in ocean floor when the rocks form (as they cool past their Curie Point). Reversals occur at intervals ranging from 10,000 years to more than 25,000,000 years. The magnetic field strength goes to zero during a reversal. We cannot predict when the next reversal will occur.

Magnetic field strength: 0.60 gauss at the magnetic poles and 0.25 gauss at the magnetic equator. A typical household magnet has a field strength of 100 gauss.

How can a magnetic field exist in Earth's core when the temperature is too hot for a bar magnet to maintain a magnetic field? The answer lies in the interaction between Earth's inner and outer cores.

Stern (2001) states: "In nature, magnetic fields are produced in the rarefied gas of space, in the glowing heat of sunspots and in the molten core of the Earth. Such magnetism must be produced by electric currents, but finding how those currents are produced remains a major challenge."

Glatzmaier (1995) states: "... the temperature of the core is too high to sustain permanent magnetism... These observations argue for a mechanism within the Earth's interior that continually generates the geomagnetic field. It has long been speculated that this mechanism is a convective dynamo operating in the Earth's fluid outer core, which surrounds its solid inner core, both being mainly composed of iron. The solid inner core is roughly the size of the moon but at the temperature of the surface of the sun. The convection in the fluid outer core is thought to be driven by both thermal and compositional buoyancy sources at the inner core boundary that are produced as the Earth slowly cools and iron in the iron-rich fluid alloy solidifies onto the inner core giving off latent heat and the light constituent of the alloy. These buoyancy forces cause fluid to rise and the Coriolis forces, due to the Earth's rotation, cause the fluid flows to be helical. Presumably this fluid motion twists and shears magnetic field, generating new magnetic field to replace that which diffuses away."

 




Lecture

PowerPoint slides: Gravity and isostacy

PowerPoint slides: Magnetism

Laboratory

Lab: nothing






 

Lab: Density


Lab Assignment (due 18 October 2017): Specific Gravity

The specific gravity was determined for a variety of rocks and minerals that represent oceanic and continental lithosphere.

Write up the results according to the assignment handed out in class and be sure to follow the proper format for writing. This assignment is worth two lab grades.

 

Class data

 

Published data

location
mineral formula
density (g/cm3)
B1-3
quartz SiO2
2.65
A6
Na-rich plagioclase feldspar NaAlSi3O8
2.62
A5
Ca-rich plagioclase feldspar CaAl2Si2O8
2.76
A7
alkali feldspar (K,Na)AlSi3O8
2.55 - 2.63
A4
biotite K2(Mg,Al)6Si6Al2O20(OH)4
2.7 - 3.3
B4
muscovite K2Al4[Si6Al2O20](OH,F)4
2.77 - 2.88
A1
olivine (Mg,Fe)2SiO4
3.222 - 4.392
A2
pyroxene Ca(Mg,Mn,Fe)Si2O6
3.22 - 3.56
A3
amphibole Ca2(Mg,Fe)4Al[Si7AlO22](OH)2
3.02 - 3.59
D3
galena PbS
7.5 - 7.6

 

 

 



2 – 6 October 2017 [Week 6]

Seismology

Seismology is the study of Earth and earthquakes using seismic waves. An earthquake releases seismic energy in the form of seismic waves. L-waves are surface waves and are the slowest seismic waves; P-waves and S-waves are body waves. P-waves are compressional waves, travel almost twice as fast as S-waves, and pass through solids and liquids; S-waves are shear waves and therefore cannot pass through liquids.

The time difference between the arrival of the first P-wave and the arrival of the first S-wave is known as the S-P interval. This difference in arrival times increases with increasing distance from the focus. Triangulation can be used to locate the focus of a seismic event. Seismic tomography is used to describe Earth's internal structure. Through our understanding of seismic waves, we have been able to identify the many layers within Earth.

The elastic rebound theory suggests that rocks at the surface respond to stress in a brittle fashion. In contrast, rocks at depth respond in a ductile fashion. The temperature and pressure increase with increasing depth – these elevated conditions of pressure and temperature favor ductile deformation. In fact, the average geothermal gradient is 30ºC/km and the average pressure gradient is 0.3 kb/km.

The Richter Magnitude Scale records the amplitude of the recorded seismic wave. An amplitude of 1 cm, at a distance of 100 km from the epicenter, is regarded as a Richter magnitude 4 seismic event. Each increase of one unit on the Richter scale corresponds to a ten-fold increase in the amplitude of the recorded seismic wave and a thirty-two-fold increase in the energy released by that event.

The Modified Mercalli Intensity Scale is a measure of what is felt on Earth's surface; it is based on a scale from I (1) to XII (12). The public is encouraged to report their observations to the USGS. The damage that results from a seismic event is based on the geology, distance to epicenter, depth of focus, and anthropogenic modifications to the land.

Learn about recent seismic activity from the USGS Earthquake Hazards Program or search the Significant Earthquake Database. Learn about some of the interesting, active research on the San Andreas fault system. See Earthscope for locations of seismometers in the US. Read about the history of destructive earthquakes in the Himalayan Mountains.

Seismicity is associated with ground motion. Poorly consolidated rocks lose their cohesive strength when subjected to the shaking associated with seismic waves and the rocks are unable to support any structures. This process is known as liquefaction. Tsunamis are large amplitude and long wavelength ocean waves initiated by the displacement of water associated with an earthquake.

See the United States Geological Survey report of seismicity in Vermont or a brief discussion of the 20 April 2002 event felt throughout Vermont. Click here for recent (the past week) seismic activity in Vermont.

Watch the sequence of seismic events that lead up to the 2011 Tohoku earthquake, also known as Great East Japan Earthquake, of Friday, 11 March 2011.

Earthquakes cannot be predicted, however, some inconsistent precursors have been identified (for example, unusual animal behavior, gas emissions, precursor seismic events, change in groundwater levels, change in resistivity, and earthquake lights with associated brontides).

Lab: seismicity

First Exam: Thursday, 5 October 2017

 




Lecture

PowerPoint slides: Seismicity

Laboratory

Lab: Seismicity




 

Lab: Seismology (pages 101-112 in the lab manual)
Properties of seismic P-, S-, and L-waves were discussed. Questions 12-20, starting on page 104, of the lab manual were addressed.


Lab Assignment (due in lab, on 4 October 2017): Location of Epicenter

Figure 7, p. 108 from the lab manual was submitted the location of the epicenter was clear, accurate, precise and defined by latitude and longitude. The time of the earthquake, and a description of how the time was determined was also submitted.



9 – 13 October 2017 [Week 7]

Fall Break — be careful.

 



16 – 20 October 2017 [Week 8]

No class on Tuesday; we will meet in lab on Wednesday and hold class on Thursday.

 

Plate Tectonics

Heat from Earth's interior drives mantle convection, volcanism, seismicity, and plate movements. The theory of plate tectonics allows us to better understand how Earth has been modified through tectonic forces. See Scotese's site for plate reconstruction animations. The central region of a large continental landmass is old and commonly referred to as a continental cratonic region. Sediment is deposited along the edges of the craton (from erosion) and may later be subjected to deformation (through collision). In addition, other landmasses (terranes) may be juxtaposed against the craton through plate motion. Click here for a model of plate motions.

Convergent Plate Boundaries

Convergent plate boundaries are associated with shallow focus compressive earthquakes (the plates are moving toward each other), deep focus tensile earthquakes (the down going lithospheric slab is falling into the mantle thereby breaking off from the major slab), and low geothermal gradients.

Young compressive plate boundaries are often associated with shallow angles of subduction. The Benioff Zone expresses the angle of subduction. The Benioff Zone is defined by the earthquake foci that occur in the brittle, down going lithospheric slab. This zone can also be modeled by seismic wave velocities (seismic waves travel faster in more rigid rocks – i.e. lithosphere rather than asthenosphere).

Volcanism associated with subduction complexes requires water to promote the melting of rocks. Water is squeezed out from the down going slab; this water interacts with the hot rock and causes melting. The water can be found as structurally bound to the mineral or in the pore spaces (including the sedimentary wedge carried down with the lithosphere). Learn more about the Cascade Mountain Range

 

Divergent Plate Boundaries

Divergent plate boundaries can be considered to be ocean floor factories. This type of plate boundary is associated with normal faults, seismic activity, volcanism, the formation of ocean basins, and high geothermal gradients. Upwelling mantle material cools at Earth's surface (but below sea level) to form ocean floor (peridotites overlain by gabbros overlain by sheeted dike complex and overlain by pillow basalts). Numerous hydrothermal vents are associated with divergent plate boundaries.

 

Hot spots

Hot spots (also known as mantle plumes) are one source of molten rock. This molten material produces volcanic islands. The hot spot beneath Iceland accounts for the presence of that island, and the Hawaiian Hot spot accounts for the distribution of the Hawaiian-Emperor Chain. Hot spots occur beneath the crust, yet the maximum depth is unknown. The permanence of hot spots (both in location and duration) is also poorly understood. Watch a video of undersea volcanic vents or see Woods Hole Oceanographic Institute videos.




Lecture

PowerPoint slides: Plate tectonics

Laboratory

Lab: Plate tectonics




 

 

Lab Assignment (due in-class 18 October 2017): Plate Tectonics

Please answer questions 12 through 26 starting on page 115 of the laboratory manual.
 

 



23– 27 October 2017 [Week 9]
Transcurrent Plate Boundaries

Transcurrent plate boundaries are commonly associated with steeply dipping faults and primarily horizontal movement; this is known as strike-slip motion. Lithosphere is not created or destroyed at this type of plate boundary; shallow focus seismic activity is common. The San Andreas Fault system is a good example of this type of plate boundary.

 

Summary of plate boundaries; there are three general types of plate boundaries:

Name Motion Type of fault Example Volcanism Seismicity Lithosphere
1. Compressional → ← reverse Himalayas, Cascade Mt. Range yes (80%) yes consumed
2. Extensional ← → normal mid-ocean spreading ridges yes (15%) yes created
3. Transcurrent side by side transform San Andreas Fault system none yes unchanged

Igneous Rocks

Volcanic activity is associated with divergent plate boundaries (15%), convergent plate boundaries (80%), and mantle plumes (5%). Volcanic (extrusive) igneous rocks have relatively small minerals (too small to be seen without a hand lens) as a result of the rapid cooling of lava, whereas plutonic (intrusive) igneous rocks have larger minerals because magma cools more slowly (the heat within the magma is retained by the country rock which acts like a blanket). Lava that cools under water forms pillow lavas.

Bowen's Reaction Series describes the minerals, rock color, crystallization temperature, and viscosity of the common igneous rocks. Similar minerals may be found in different types of rocks because of dissimilar cooling rates (for example, compare basalt to gabbro, or rhyolite to granite). Different minerals, with similar cooling rates, would also produce different types of rocks (for example, compare gabbro to granite, or basalt to rhyolite). All rocks in Bowen's Reaction Series are igneous rocks because the minerals form through cooling of molten material (lava or magma).

Viscosity is a measure of a material's ability to resist flow. Low viscosity lavas, such as basalt, flow gently onto Earth's surface. High viscosity lavas, such as rhyolitc or andesitic lavas, commonly produce explosive volcanic events.

Volcanoes represent yet another of Earth's safety release valves. Volcanoes release immense heat, quickly, and locally. View the current status of Kilauea, movies of Kilauea, other Hawaiian volcanoes, or the Cascade Volcano Observatory. Another good resource is the Electronic Volcano (hosted by Dartmouth) or the Global Volcanism Program (hosted by the Smithsonian). See the NOAA Significant Volcanic Eruption Database or the USGS listing of US volcanoes that are currently above background level or the Smithsonian Weekly Volcanic Activity Report. The US Geological Survey has an online photo glossary (and real-time video) of volcanic terms, or read about Yellowstone's future. An undersea volcano erupts near Tonga on 18 Mar 09, see the pictures.

Common basaltic lava flow textures:

Intrusive Features:

Types of Volcanoes:

Eruptive Products:

Eruptive Styles:

Volcano information:

 



Lecture

PowerPoint slides: Igneous Rocks

Laboratory

Lab: Plate tectonics 2





 

Lab Assignment (due 1 November 2017): Plate tectonics and the origin of magma

  • Please answer questions 15 through 19 starting on page 137 of the laboratory manual; for Question 16c specify the direction – use numbers (a map is not required).
  • Draw pictures when necessary.
  • Be sure to use complete sentences for all responses – either write out all equations (using a pen) or fully explain the method.
  • Type the responses and use one staple to hold together the typed text.

 



30 October – 3 November 2017 [Week 10]

Science Internship Presentations
Tuesday, 7 November 2016 (6:30 to 8:00 p.m.)

Two points of extra-credit.

Join us in Bentley 206 for the Science Internship Presentations by students in the Department of Environmental and Health Sciences. Please do the following to receive credit:

Create an appropriate cover page for the report. For each of the presentations please include the following information:

  • Name of presenter.
  • Title of presentation.
  • Describe the internship opportunity and what was accomplished.
  • Critique the presentation.

Be sure to number the pages (using the computer), write properly, and submit a well-formatted and clear report.

Use one staple to hold all pages together.

Submit the report, at the start of class, on Tuesday, 14 November 2017.

 

Weathering

Rocks can be physically or chemically weathered. Physical weathering affects the entire solid by the following agents: root pry, frost riving, human activity (walking and ATV), flowing water, winds (sand blasting), daily thermal expansion, and burrowing organisms. Physical weathering produces smaller rock fragments (also known as clasts, sediments, or particles).

Chemical weathering affects the surface of solids by the following agents: acid rain, organic acids (humic acids), and chemically active water. Carbonates (limestone and marble) are more easily weathered by acid rain than silicates (igneous rocks). Small particles have a higher surface area-to-volume ratio than large particles so chemical weathering is more effective at smaller sizes (that is why granulated sugar dissolves more readily than a sugar cube).

See pictures of monuments at Hope Cemetery in Barre, VT; the granite monuments are spectacular and not affected by acid rain.

Rainwater in New England is acidic. The acid is neutralized in lakes by the carbonate minerals (calcite) that make up the carbonate sedimentary rocks (limestone) and the carbonate metamorphic rocks (marble).

 

Weathered material is transported in a variety of ways by the agents of wind, water, or ice:

 

Sedimentary Structures

Bi-directional transport (i.e. waves) produces symmetrical ripples. Transport in one direction (by streams or wind) produces asymmetrical ripples. The ripples migrate in the transport direction by removing sediments on the upstream, stoss, (gentle) side and depositing sediments on the downstream, lee, (steep) side of the ripple. This process produces cross-bedding. The thickness of the cross-bedded units produced by streams is on the centimeter scale (and the grains are polished), tidal channels on the tens of centimeters scale, and those units deposited by winds are on the meter scale (and the grains are frosted by pitting with other grains).

Graded beds are represented by a layer of clastic sedimentary rock where the larger particles are found toward the base of the unit and the smaller particles are found toward the top of the unit. Graded beds can form in a stream environment or under conditions where the energy level decreases over time.

The following sedimentary structures can be used as way-up indicators: cross-bedding, sole markings, asymmetrical ripples, symmetrical ripples, rain drop impressions, trace fossils, mudcracks, footprints, mud volcanoes, flame structures, graded beds, mullions, and tool markings. 

Through observation of the properties of the sediments one should be able to determine the environment in which the rocks were deposited. Geologists are basically detectives that uncover clues that elucidate the geologic history of an area.

 



Lecture

PowerPoint slides: Weathering

PowerPoint slides: Sedimentary structures

Laboratory

Lab: Glaciers

 




 

Lab: Glaciers

Glaciers have sculpted the landscape for hundreds of millions of years; the most recent glaciation (that ended about 10,000 years ago) is responsible for much of the topography and all of the gravel pits in Vermont. Learn about ancient glacial Lake Hitchcock that is associated with the sedimentary cover in Vermont.

Glaciers advance when more snow accumulates above the snowline than that which is lost in the zone of ablation. Consider advancing glaciers to act like conveyer belts that pluck rocks from beneath the ice and transport the material downhill.

Glacial striations, gouges, roché moutonee, chatter marks, and indicator fans allow geologists to work out the direction of glacial transport. Some of the topographic features attributed to glaciation include: horns, arêtes, paternoster lakes, U-shaped valleys, and spectacular waterfalls. Glaciers also provide a wide variety of depositional environments. 

There are some excellent web sites related to glaciology: ICSU World Data Center, the National Snow and Ice Data Center or watch NOVA's slide show that traces the evolution of freshly fallen snow. Click here for a rich resource related to glaciers.

 

Lab Assignment (due 8 November 2017): Glaciology

Please answer Questions: 20-22 and Figure 14; and Questions 31-35 and Figure 17 (Pages: 143-161).
Type the responses and use complete sentences (be sure to identify the question).
Use one staple to hold all sheets together.

 

 


6 – 10 November 2017 [Week 11]
Soil

Soil is the place where atmosphere, biosphere, hydrosphere, and lithosphere interact. Life is vital to soil and soil is vital to life. It is a complex biogeochemical material – a dynamic ecosystem. Soil is produced on the land surface by the interaction of living organisms and organic matter with weathering products.

Soils comprise decayed organic materials, inorganic materials, organisms, moisture, and air. The texture of soil is based on the ratio of sand : silt : clay and is named by plotting these ratios on a triangular diagram. Soil texture plays a significant role in the hydraulic properties of soil. Soil erosion throughout the world is occurring at astonishingly high rates. The soil profile comprises five master horizons (O, A, B, E, C, and R) and numerous subhorizons.

Groundwater

The hydrologic cycle depicts water flow through Earth's systems through evaporation, condensation, evapotranspiration, runoff, infiltration, and groundwater flow. Groundwater is found below the water table in aquifers; aquifers are porous and permeable rock units that store and transmit water. The water table is the depth at which the pores are saturated (the zone of saturation). The water table is a surface at or below ground level that separates the unsaturated zone above from the saturated zone below. It is a subdued replica of the topography.

One factor that affects groundwater quality depends directly on the rocks that comprise the aquifer. View the EPA list of drinking water contaminants and maximum contaminant levels. The Vermont Department of Health can test your water for a large number of contaminants. Click here to find out what is in the groundwater in your area. Learn about the quality of Vermont's groundwater.

The VT Department of Health Lab is not certified to conduct PFOA water testing. You can find some information about the PFOA contamination in the Bennington area here: http://dec.vermont.gov/commissioners-office/pfoa/communities and find a list of EPA approved Labs for PFOA testing through this link: http://dec.vermont.gov/sites/dec/files/co/pfoa/documents/WellTesting-Outside.pdf.



Lecture

PowerPoint slides: Groundwater

Laboratory

none




Lab: Porosity and permeability

Some properties of the rock fragments that are of interest to geologists include: roundness, sphericity, size, sorting, surficial features, composition, and packing. The names of clastic sedimentary rocks are based upon the size and composition of the particles that make up the rock, whereas the names of igneous rocks are based upon the size composition of the minerals that make up the igneous rock. See the concept map related to sedimentary rocks.

Many of the properties noted above affect either porosity or permeability (or both). Porosity is a measure of the percent of void space in a solid; porosity values are expressed as a percentage. Pores can hold liquids or gases. When the pores are interconnected the rock is said to be permeable. Liquids or gases can move through permeable rocks.

 

Lab Assignment (due 29 November 2017): Porosity and Permeability

In lab, we measured the porosity and permeability of various sediments. Use the information (and data) gleaned in lab and describe the relationship between porosity, permeability, packing, particle size, and sorting. In the discussion, account for the range of values obtained in lab and discuss the factors that could have led to the wide range of results. Be as specific as possible and include your own results (even if they did not fit the grand scheme). Follow the guidelines on the handout. Be sure to include a discussion of your observations (including problems, individual observations, and group trends) and interpretations (trends and variability in results). Remember, follow the guidelines.

 

Class data

Note: beware of edge effects with large sediments and pores filled with air for small sediments.

 

 


13 – 17 November 2017 [Week 12]
Oceans

Seventy-one percent of Earth's surface is covered by oceans. Oceanic water is saline (34.72 ppt or 3.472%), dense (1.025 g/cm3), and freezes at -1.775 oC. On Sunday, 25 March 2012, James Cameron descended in a custom-designed, vertical submarine to the bottom (11 km) of the Mariana Trench.

 

Eustacy

Global sea level change is known as eustatic changes. The major causes of eustatic changes could be i) melting of glacial ice caps that adds more water to the oceans, ii) elevated ocean water temperatures that result in increased volume of ocean water, and iii) increased oceanic spreading rates that displaces water onto land. Eustatic changes (global sea level changes) are associated with transgressive and regressive sequences; isostatic changes (emergence and submergence) may also be related to these sequences. Possible causes of eustatic change: warming ocean waters, increased tectonic activity (primarily spreading), and the melting of glaciers.

When a stream enters a standing body of water the larger particles are deposited near shore and the finer particles carried farther away from shore where the energy is lower. As sea level rises, the same processes occur, but in a different location. The result is a transgressive sedimentary sequence (a fining upward sequence) indicative of sea level rising.

Local isostatic changes (land moving up or down) would have an effect on local sea level changes; local sea level changes are not eustatic changes.

 

Tides

There are generally two high tides each day because Earth rotates once on its axis each day. The lunar tide is about 2.17 times stronger than the solar tide. When the sun and moon are aligned (new and full moon), the tides are the greatest (also known as the spring tides). During the first and third quarters, the gravitational attraction by the moon and the sun is oriented perpendicular to each other so the tides are not as great (also known as the neap tides). Perigee, and the altitude of the moon with respect to the ecliptic during a new or full moon (syzygy), also play significant roles in tidal height. Ocean currents and the geometry of the ocean basin (or bay) also affect the height of the tides. The Bay of Fundy has a significant tidal range. NOAA/NOS presents tidal range predictions for the US; also see the astronomical data related to tides. See a 3-d animation of the orbits of the sun, Earth and moon.

Second Exam: Thursday, 16 November 2017


Lecture

PowerPoint slides: Tides

Laboratory

none




Lab: Petrographic Microscope

Lab Assignment (due in lab on 15 November 2017): Rock Texture

In-class assignment related to rock texture and mineralogy.

Use of petrographic microscope to identify rocks by texture and mineralogy. Petrographic microscopes use polarized light. The interaction of polarized light with thin sections of rock (30 microns thin) yield diagnostic optical properties (and vivid colors).

Click here to see how thin sections are made.


20– 24 November 2017 [Week 13]
Thanksgiving Break—stay safe.



 

Final Exam: Tuesday, 18 December 2017 at 10:30 a.m.

 


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