Exam 2 Questions Flashcards
Magnetic Declination Vs. Magnetic Inclination
Declination - north vs true north
Inclination - angle between horizontal plane and pole
What fossil evidence did Wegner cite as evidence that the continents had all once been amalgamated together?
land dwelling species that existed during the late Paleozoic and early Mesozoic Eras
What glacial evidence did Wegner cite as evidence that the continents had all once been amalgamated together?
Glacial till and striation in south America, Africa, India, and Austrialia
Define the meaning of the term “paleomagnetism?”
A record of Earth’s magnetic field in the past
When magma cools and crystalizes at mid-ocean ridges, what mineral commonly aligns its magnetic field with Earth’s magnetic field?
a
What is meant by an “Apparent Polar Wander Path?”
a
What are the principal landforms that occur in the oceans?
Mid Oceanic Ridges
Magnetic Anomalies occur on the sea floor because of changes in Earth’s magnetic field through time. What is the nature of that change?
Change in North and South Pole
Magnetic Anomalies aren’t random, but have a particular symmetry. Describe that symmetry.
Each side of the mid oceanic ridge is a mirror of the other side.
Where are the youngest rocks in the oceans always found?
Near the mid oceanic ridge.
What geologic processes take place at the edges of the “tectonic plates?”
subduction
Why can we use the world-wide distribution of earthquakes to define the “edges” of the tectonic plates?
Active plate boundaries
The “Moho” is the boundary between the Earth’s crust and mantle. How do geologists know this boundary exists?
The Mohorovicic discontinuity refracts p and s waves.
What does “lithosphere” consist of?
Crust and Upper Mantle. Peridotite
How does continental lithosphere differ from oceanic lithosphere?
Oceanic - mafic rock and is denser thank Continental
How do geologists know that there is a bottom to the lithosphere?
The lower mantle is liquid
What is the bottom of the tectonic plates?
a
What are “Hot Spots?”
aunder
Where do Hot Spots form?
a
Do Hot Spots move as the tectonic plates move?
Hot Spots are stationary
What processes takes place as continents undergo rifting?
Divergent plates
Are there continents that are undergoing rifting today (where?) or is this only a process that happened in the past?
East African Rift
Why does continental lithosphere never subduct beneath oceanic lithosphere?
Oceanic lithosphere is more dense.
What landform in the oceans forms where subduction is taking place?
trenches
What is the difference between an earthquake focus (or hypocenter) and an earthquake epicenter?
hypocenter is the point within the earth where an earthquake rupture starts. The epicenter is the point directly above it at the surface
What is earthquake magnitude a measure of?
The magnitude is defined as the logarithm of the ratio of the amplitude of waves measured by a seismograph to an arbitrary small amplitude. An earthquake that measures 5.0 on the Richter scale has a shaking amplitude 10 times larger than one that measures 4.0, and corresponds to a 31.6 times larger release of energy.
How can the distribution of earthquakes be used to define the geometry of subducting oceanic lithosphere?
a
What is an “Accretionary Prism?”
sedimentary buildup near a subduction zone
What is the geometrical relationship between subduction zones and volcanos?
volcanic arc: the plate melts by the process of friction and partial melting which is caused by the oceanic liquid( water) trapped within the plate, it melts part of the lithosphere on which the plate floats on, and produces magma
What type of plate motion occurs along Transform Boundaries?
side by side
What are the two principal mechanisms causing the plates to move?
Ridge Push, Slab Pull, Convective flow
For the plate reconstructions I showed you in class, how do we know where the different continents were at different times in the past?
magnetic inclination
What is the difference between bedrock and surficial materials?
Bedrock - ledge layer, surficial: soil
Give several examples of materials that would be surficial materials.
Soil
What is the difference between a mineral and a rock?
mineral is a single composite chemical crystal, rocks have multiple
What is the definition of a mineral?
homogeneous, natural, inorganic, solids, chemical, crystal
What are the 8 most common elements in Earth’s crust?
oxygen silicon aluminum iron calcium sodium potassium magnesium
How are the different groups or classes of minerals defined, i.e. how are the silicate minerals different from the carbonate minerals different from the sulfide minerals, etc.?
a
What is an ion?
a
What is an ionic complex like SiO4?
a
How can you distinguish quartz from feldspar?
feldspar three cleavage planes
How can you distinguish biotite mica from any of the other dark-colored minerals?
biotite is black mica and has one cleavage plane
Which groups of minerals tend to be ore minerals for different metals?
a
Which group of minerals occurs in bones and teeth?
a
Do rubies and sapphires contain any exotic chemical elements?
a
What group of minerals is the larges carbon reservoir on Earth?
a
What mineral has been utilized by many plants and animals to build their shells and skeletons?
a
Why is Strontium-90 particularly dangerous to people?
a
Why is the mineral apatite being considered as a possible place to store Strontium-90?
a
How are igneous rocks uniquely different from sedimentary and metamorphic rocks?
a
How are sedimentary rocks uniquely different from igneous and metamorphic rocks?
a
How are metamorphic rocks uniquely different from igneous and sedimentary rocks?
a
How can igneous rocks transition into sedimentary rocks?
a
How can metamorphic rocks transition into igneous rocks?
a
How can sedimentary rocks transition into metamorphic rocks?
a
What type of rocks makes up most of the Champlain Valley of Vermont?
a
What type of rocks makes up most of the mountains in Vermont?
a
What is magma made of?
a
What is the geothermal gradient?
a
Is the geothermal gradient linear?
a
What are the sources of heat that comes from the Earth?
a
What happens to the melting point of most rocks as the pressure rises?
a
What happens to the melting point of most rocks if water and other volatiles are present?
a
Explain the process of decompression melting.
a
In what plate tectonic environments does decompression melting occur?
a
In what plate tectonic environment is the addition of volatiles an important process producing magma?
a
In what plate tectonic environment is it common for very hot magma to melt rocks with a lower melting temperature?
a
Igneous rocks with an aphanitic texture (fine grained) usually form where?
a
Igneous rocks with a phanerited texture (coarse grained) usually form where?
a
Igneous rocks with a porphyritic texture usually form where?
a
How does volcanic glass form?
a
What are pyroclastic rocks and how do they form?
a
With regard the classification of igneous rocks, what is meant by the term “silica content?”
a
How do felsic, intermediate, mafic, and ultramafic rocks differ one from another?
a
What is an “Ophiolite Sequence?”
a
At a divergent plate boundary, how and where do ultramafic rocks form?
a
What part of the oceanic lithosphere do ultramafic rocks form?
a
How do the minerals “serpentine” and “talc” form from ultramafic rocks?
a
What is asbestos?
a
Does all asbestos form from the same mineral?
a
How has asbestos been used in the past?
a
What are the health risks associated with exposure to asbestos?
a
Are all types of “exposure” to asbestos equally dangerous?
a
What is soapstone and how has it been used?
a
What are some of the principal conduits by which magma flows from deep magma chambers towards Earth’s surface?
a
What is the difference between a dike and a sill?
a
Where in the oceanic lithosphere do sheeted dikes form?
a
What is the evidence that dikes may form from separate pulses of magma?
a
What is the relationship between the orientation of dikes and the direction Earth’s crust extends when those dikes intrude?
a
Why are dikes usually oriented radially around volcanos, like spokes around a bicycle wheel?
a
Where do pillow basalts form?
a
What is unique about the shape of pillow basalts that allows one to determine what direction was “up” at the time those basalts formed?
a
What is the composition of igneous rocks that typically form at convergent plate boundaries?
a
Where are most of the stocks and batholiths in Vermont?
a
When you find stocks and batholiths of intermediate to felsic igneous rock, what type of plate boundary used to exist in this area?
a
What are the different processes that are utilized to quarry granite?
a
Why is the Barre granite valuable?
uniform
What is silicosis?
is a lung disease caused by inhaling crystalline dust composed of finely ground quartz and feldspar. Exposure to silica dust is especially high among granite workers. The old finishing sheds, where granite was cut and polished, didn’t have any ventilation systems and so were constantly filled with dust.Particles in the lungs create scar tissue and the scars for nodules 10 to 20 years of exposure.
In an area of igneous rock, how would you know that you were in a “Pegmatite?”
a
How do pegmatites form?
coarse grained rocks formed by the solidification of steamy melt
What are the common minerals found in pegmatites?
a
Why are some of the minerals found in pegmatites rare and potentially valuable?
concentrated large crystals
What are volcanos composed of?
a
