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ESC1000 FSU Yang Wang Midterm
Terms in this set (73)
Contrast the geocentric and heliocentric Universe concepts.
Geocentric-Earth was the center of the universe
Heliocentric-non-circular orbits, sun is the center of the solar system
Describe how Foucault's pendulum demonstrates that the Earth is rotating on its axis.
demonstrates that the earth is rotating on its axis because he set a heavy pendulum attached to a string and noted that the plane it rotated on was perpendicular to earth's surface and plane rotated along the vertical axis. 1st law of motion- object in motion remains in motion - earth in motion
How did Eratosthenes calculate the circumference of the Earth?
Used the sun's distance, rays, height of pole, and its shadow
Erastothenes used the lengths of shadows to figure out how high in the sky the sun was in a certain place on a certain day. (His hometown Alexandria on the summer solstice) He knew of another place (Syene on the other side of Egypt) where there was no light at all on the same day. This meant the sun was straight overhead He found out the difference b/w the 2 places and used geometry to figure out the rest.
Imagine you hear the main character in a cheap science-fiction movie say he will "return 10 light years from now." What is wrong with his usage of the term "light year"? What are light years actually a measure of?
Light year is a term for distance not for time
Describe how the Doppler effect works.
waves compress with relative motion
What does the red shift of the galaxies tell us about their motion with respect to the Earth?
the galaxies are moving away from us
Light from distant galaxies appeared "red shifted." (Edwin Hubble- Hubble's Law)
Briefly describe the steps in the formation of the Universe and the solar system.
The Big Bang, then atoms bonded as the universe cooled(first was helium and hydrogen)
How is a supernova different from a normal star?
supernovas are made of elements with atomic numbers greater than 26.
A supernova is a stellar explosion that briefly outshines an entire galaxy, radiating as much energy as the sun, or any ordinary star is expected to emit over it's entire life span; before then fading.
Why do the inner planets consist mostly of rock and metal, but the outer planets mostly of gas?
the outer planets spun quicker trapping the gas inside during formation
Solar winds blew away most gas from inner planets as well
Why do astronomers consider the space between planets to be a vacuum, in comparison with the atmosphere near sea level?
In interstellar space therer is a vaccum with a virtual absence of matter while the atmosphere at the sea level is bursting with matter.
How does the Earth's magnetic field interact with solar wind? Be sure to consider the magnetosphere, the Van Allen radiation belts, and the aurorae.
-The magnetic field protects the Earth from solar wind (high-velocity charged particles emitted by the Sun). It distorts the solar wind into a teardrop, pointing away from the Sun. It deflects (almost) all of the particles so that they do not reach the Earth's surface. The region inside this teardrop-shaped magnetic shield is called the magnetosphere.
-Van Allen radiation belts contain solar wind particles and cosmic rays (nuclei of atoms emitted from supernova explosions) that were moving so fast they were able to penetrate the weaker (outer) part of the magnetic field, but were stopped by the stronger field closer to Earth. These particles and rays are now trapped in between the weaker and stronger magnetic fields.
-The Van Allen belts protect life from radiation, however, some of the particles occasionally escape (most notably near the poles) and interact with gasses in the upper atmosphere, causing such phenomena as the Northern Lights, called aurorae.
What is the Earth's atmosphere composed of, and how does it differ from the atmospheres of Venus and Mars? Why would you die of suffocation if you were to eject from a fighter plane at an elevation of 12 km without taking an oxygen tank with you?
The Earth's atmosphere is composed of mostly nitrogen (78%) and oxygen (21%), with 1% of other gasses. Earth's atmosphere differs from Venus and Mars in the involvement of air pressure. The weight of overlying air squeezes on the air below, pushing gas molecules in the air below closer together. This explains why the air becomes thinner the higher the elevation. Fun fact - 99% of atmospheric gas lies below 50 km. Humans cannot live long at an elevation greater than 5.5 km, which is why the pilot would suffocate at 12 km with no oxygen tank (because there isn't enough oxygen at that height).
What is the proportion of land area to sea area on the Earth? From studies of the hypsometric curve, approximately what proportion of the Earth's surface lies at elevations above 2 km?
-The Earth is approximately 70% surface water and 30% land.
-A hypsometric curve is a graph that plots surface elevation on the vertical axis and the percentage of the Earth's surface on the horizontal axis. Most land surface lies around a kilometer of sea level, leaving a very small portion of Earth's surface at a high elevation.
What are the two most abundant chemical elements in the Earth? Describe the major categories of materials constituting the Earth. What are the two most abundant chemical elements in the Earth's crust?
The two most abundant chemical elements in the Earth are Iron and Oxygen, however silicon and magnesium make another large portion of the elements that make up the Earth (Oxygen ~ 30.1%; Iron ~ 32.1%; Silicon ~ 15.1%; Magnesium 13.9%; Other ~ 8.8%)
The major categories of materials constituting the Earth:
contains carbon; found in living organisms
A solid, natural substance in which atoms are arranged in an orderly pattern.
Solid; atoms not arranged in orderly pattern
aggregates of mineral grains/masses of natural glass
loose mineral grains
Solids of metal atoms (iron, aluminum, copper, tin)
Alloys are mixes of more than one type of metal atom
form when solid materials melt into liquids (like ice cubes melting into water)
Easily transform into gas at (relatively) low temperatures found at the Earth's surface
What observations led to the realization that the Earth is largely solid and that theEarth's mass is largely concentrated toward the center?
Beginning in 1776, scientists began trying to calculate the density of the Earth. They soon realized that the average density of Earth exceeds that of its surface rocks, meaning that the Earth is made entirely of rock and that there are no large, empty caverns underneath the surface - Earth was not hollow.
In 1896, a physicist (Emil Wiechert) realized that to meet the calculated density, the interior of the Earth must include metal.
Went on to describe that there was a metallic ball in the center (the core) with a rocky shell surrounding the core (the mantle).
Additional insights came from the study of ocean tides (in response to the Moon & Sun)
If core was liquid, the liquid in the core would move with the tides
What are the principal layers of the Earth? What happens to earthquake waves when they reach the boundary between layers? How do the inner core and outer core differ from one another?
How do temperature and pressure change with increasing depth in the Earth? Be sure to explain the geothermal gradient.
They both increase
What is the Moho? How was it first recognized? Describe the difference between continental crust and oceanic crust. Approximately what percentage of the Earth's diameter is within the crust?
The Moho is the crust-mantle boundary, first recognized by an abrupt change in seismic-wave velocities. Continental crust is thicker, less mafic, and more variable in chemistry than oceanic crust.
What is the difference between the lithosphere and the asthenosphere? Be sure to consider material differences and temperature differences. Which layer is softer and flows easier? At what depth does the lithosphere/asthenosphere boundary occur? Is this above or below the Moho?
The lithosphere is relatively cool and rigid compared to the hot, soft asthenosphere, which flows more readily.
The lithosphere consists of the crust (oceanic basalt and gabbro, or continental granite) plus the uppermost mantle (peridotite) down to a depth of about 100 to 150 km.
This boundary lies below the Moho. The asthenosphere is only molten (liquid) in places.
What was Wegener's continental drift hypothesis?
Wegener hypothesized a former supercontinent Pangaea
•Based on abundant evidence.
•"Fit" of the continents.
•Location of glaciations.
•Rock type and structural similarities.
How does the fit of the coastlines around the Atlantic support continental drift?
The pieces of the continents joined together like a jigsaw puzzle with few overlaps and gaps.
Explain the distribution of glaciers as they occurred during the Permian period.
Permian glacial tills found on 5 continents.
The tills in Africa and India are now near equator.
How does the evidence of equatorial climatic belts support continental drift?
By placing pangaea over the permian south pole, tropical coals, tropical reefs, subtropical deserts and evaporates can be predicted correctly.
Was it possible for a dinosaur to walk from New York to Paris when Pangaea existed?Explain your answer.
Why were geologists initially skeptical of Wegener's continental drift hypothesis?
There was not a force strong enough to move the continents.
Describe how the angle of inclination of the Earth's magnetic field varies with latitude. How could paleomagnetic inclination be used to determine the ancient latitude of a continent?
Describe how the angle of inclination of the Earth's magnetic field varies with latitude.
Inclination of the Earth's magnetic field changes from 0 deg. at the equator to 90 deg. at the magnetic pole
Inclination increases towards the magnetic pole
Magnetism is frozen into rocks at the time of their formation
Describe the basic characteristics of mid-ocean ridges, deep-ocean trenches, and seamount chains.
Mid Ocean- elongated submarine mountain range.
Deep ocean trench- deep troughs in the ocean.
Seamount- Isolated submarine mountains.
Describe the hypothesis of sea-floor spreading.
Molten rock rose upward beneath mid-ocean ridges and the material solidified to create oceanic-crust. the new floor moved away from the ridge
Heat flow and seimicity are concentrated around parts of the oceanic fractures zones. MOR axis, and deep ocean trenches.
How were the reversals of the Earth's magnetic field discovered? How did they corroborate the sea-floor-spreading hypothesis?
Through magnometers, as you travel away from mid-ocean ridges the polarity shifts from north to south showing that the sea floor has been spreading by the time's lines of the magnetic reversals
What is a marine magnetic anomaly? How is it detected?
Alternating polarity bands of seafloor gathered by manometers towed by boats. It is a variation in the strength of Earth's magnetic field caused by magnetism in rocks of the ocean floor.
Describe the pattern of marine magnetic anomalies across a mid-ocean ridge. How is this pattern explained?
The pattern is SYMMETRICAL because the sea floor spread away from the mid-ocean ridge accompanied with polar reversals.
Did drilling into the sea floor contribute further proof of sea-floor spreading? If so, how?
Yes, as holes were drilled into the sea floor progressively getting farther away from the mid-ocean ridge, the sediment layer became thicker and thicker which only occurs if the sea floor is older and has been accumulating sediment longer.
Dating methods indicate that the oldest rocks on continents are almost 4 billion years old, whereas the oldest ocean floor is only 200 million years old. Why?
What are the characteristics of a lithosphere plate?
- made of both crust AND the upper mantle
- is in motion over the asthenosphere
- is rigid
- movement described as tectonic plates
How does oceanic crust differ from continental crust in thickness, composition, and density?
- 7-10 km thick (crust)
- a basaltic crust
- 35-40 km thick (crust)
- less dense
- varies in thickness
- a granitic crust
- more buoyant
Contrast active and passive margins.
Margins near plate boundaries are "active."
Margins far from plate boundaries are "passive."
What are the basic premises of plate tectonics?
Sea-floor spreading + continental drift = Plate Tectonics • lithosphere is divided into discrete rigid plates, these plates move with respect to each other
• plates ride on weak asthenosphere (upper part of the mantle)
• mid-oceanic ridges o generation of new lithosphere
• subduction zones o destruction of old lithosphere
How do we identify a plate boundary?
- Locations on Earth where tectonic plates meet.
- Identified by concentrations of earthquakes.
- Associated with many other dynamic phenomena.
- Plate interiors are almost earthquake-free.
Describe the three types of plate boundaries.
Divergent - Tectonic plates move apart; mid-ocean ridge
Sea-floor spreading causes plates to move apart.
Magma wells up to fill the gap.
Magma cools, adding material to each plate.
Convergent - Tectonic plates move together.
Ocean to Ocean... oceanic arc
Continent to Continent... mountain ranges
Ocean to Continent... volcanic arc
Transform - Tectonic plates slide sideways; earth quakes
How does crust form along a mid-ocean ridge?
When the crust breaks open because of the plates spreading apart, hot magma bubbles to the surface. the magma is converted into rock.
What is a Wadati-Benioff zone, and how does it help to define the location of subducting plates?
- One plate dives back into the mantle (subduction).
- The subducting plate descends at an average of 45°.Plate descent is revealed by a belt of earthquakes -Wadati-Benioff zone
- Earthquakes deepen away from trench
A subducting plate's path (called the Benioff-Wadati [or Wadati-Benioff] zone) is defined by numerous earthquakes along a plane that is typically inclined between 30° and 60° into the mantle.
Describe the major features of a convergent boundary.
Convergent boundary- there can be trenches where subduction occurs. There are usually volcanos lining the boundary.
What is a triple junction?
Triple junction is where 3 points of a plate meet.
How is a hot-spot track produced, and how can hot-spot tracks be used to track the past motions of the overlying plate?
A hot spot is a desolate volcano that erupts again when the plate produces movement. The hot spot is usually places far away from the fault line. We can see where a plate might have traveled because of the placement of various hot spots around the ocean
Describe the characteristics of a continental rift, and give examples of where this process is occurring today.
Continental lithosphere spreads apart and the brittle crust breaks to make rifts. The break could be so large that it separates the mass of land it is underneath, making the mass into two separate pieces.
Examples: San Andreas Fault
Basin and Range province on Western U.S.
Describe the process of continental collision, and give examples of where this process has occurred.
When two continental plates collide, the crust crumples and thickens, creating high mountains and a wide plateau
Ex) Himalayas and Tibetan Plateau
Discuss the major forces that move lithosphere plates.
Plate Tectonics- are responsible for moving the plates.
Convection- the magma rises from a crack in the crust and the magma cools and goes through the process of becoming rock and while the rock moves farther away as a result of more magma/rock formation, the older rock is eventually pulled back under the crust.
Ridge Push Force- the weight of new rock is pulled down by the force of gravity, causing the two plates to move away from each other.
Slab pull force- instead of breaking or wrinkling, the plate slides right under the other plate.
Can we measure present-day plate motions directly?
Yes, plotting plate motion relative to a fixed spot in the mantle or by measuring volcanoes ages/distances along a hotspot track.
What is a mineral, as geologists understand the term? How is this definition different from the everyday usage of the word?
To a Geologist a mineral is a NATURALLY OCCURRING SOLID, formed by geologic processes, that has a CRYSTALLINE structure and a definable CHEMICAL COMPOSITION. There are synthetic minerals produced in factories, but geologist do not consider these real minerals.
Why is glass not a mineral?
A mineral is crystalline, and glass is not. In a mineral: atoms, ions, or molecules are ordered into a crystal lattice, like soldiers standing in formation, those in a glass are arranged in small clusters or chains that are neither oriented in the same way nor spaced at regular intervals.
Salt is a mineral, but the plastic making an inexpensive pen is not. Why not?
Plastic is not created by a natural geologic process.
Diamond and graphite have an identical chemical composition (pure carbon), yet they differ radically in physical properties. Explain in terms of their crystal structure.
Diamond-Strong covalent bonds; hardest mineral.
Graphite - Weak Van der Waals bonds; softest mineral.
Why do some minerals occur as beautiful euhedral crystals, whereas others occur as anhedral grains?
Minerals occur as EUDRHAL crystals because their growth is uninhibited so that it displays WELL-FORMED CRYSTAL FACES.
Other minerals that are without well-formed crystal faces are called ANHEDRAL. They become anhedral because typically the GROWTH of minerals is RESTRICTED in one or more directions because of existing crystals that act as obstacles. In these cases minerals grow to fit the space that is available.
List and define the principal physical properties used to identify a mineral.
- Color: Color varieties often reflect trace impurities.
Olivine is olive green.
Azurite is always blue.
Some minerals may exhibit a broad color range. Quartz (Clear, white, yellow, pink, purple, gray, etc).
- Streak: Color of a mineral crushed on unglazed porcelain.
Congruent streak - Streak color same as mineral.
Magnetite - Black mineral; black streak .Incongruent streak - Streak color different than mineral.
Chromite - Black mineral; greenish-brown streak.
- Hardness: Scratching resistance of a mineral.
Hardness compared to the Mohs Hardness Scale.
metallic --> Highly reflected and "metal colored"
Vitreous: Shines like a glass
Pearly: Whitish iridescence (like a pearl) Resinous: Dull shine (like wax)
Earthy (Dull): Surface doesn't reflect light
- Specific gravity
• Related to density (mass per volume).
• Mineral weight over weight of equal water volume.
• Specific gravity is "heft"- How heavy it feels.
- Crystal habit: shape of a single well-formed crystal.
Crystal habit is the ideal shape of crystal faces.
Ideal growth requires ideal conditions.
Give the chemical formulas of the following minerals: quartz, halite, calcite, and fluorite.
What holds atoms together in a mineral?
5 recognized types of bonds.
Van der Waals.
How can you determine the hardness of a mineral? What is the Mohs hardness scale?
This test compares the resistance of a mineral to being scratched by ten reference minerals known as the Mohs Hardness Scale.
How do you distinguish cleavage surfaces from crystal faces on a mineral?How does each type form?
Cleavage: A mineral that regularly breaks along a predetermined plane has cleavage.
Cleavage planes can be repeated, crystal faces are a single surface
What is the prime characteristic that geologists use to separate minerals into classes?
Their Dominant Anion
What is the principal anionic group in most familiar silicate minerals? On what basis are silicate minerals further divided into distinct groups?
- Rock-forming minerals
- The silicate structure
- Silicon Oxygen Tetrahedron
What is the relationship between the way in which silicon-oxygen tetrahedra bond in micas and the characteristic cleavage of micas?
Micas tend to cleave between the silicon-oxygen structures, rather than across them because the silicon-oxygen bonds are strong. The micas' sheet structure causes them to cleave flat plates.
How do sulfate minerals differ from sulfides?
Why are some minerals considered gems? How do you make the facets of a gem?
To qualify as a gem, the specimen should be hard and tough to resist scratching and have beautiful clarity color or 'fire'. Value is based on rarity and rare quality.
How is the process of freezing magma similar to that of freezing water?How is it different?
They are both solidified, water has low temps, magma has high temps.
Describe the three processes that are responsible for the formation of magmas.
-Partial melting from pressure release
Why are there so many different types of magmas?
Because of the different percentages of silica partial melting, assimilation, magma mixing, fractional crystallization.
Why do magmas rise from depth to the surface of the Earth?
Because magma is less dense, so buoyancy drive it upward and the pressure of overlying rock squeezes magma upwards.
What factors control the viscosity of a melt?
-Temperature- hotter lower viscosity
-Volatiles- lower viscosity
-Silica- more high viscosity
What factors control the cooling time of a magma within the crust?
-Extrusive setting- cool at or near surface(quick)
-intrusive- cool at depth(slow)
How does grain size reflect the cooling time of a magma?
-spherical bodies- cool slower
-tubular bodies- cool faster
What does the mixture of grain sizes in a porphyritic igneous rock indicate about its cooling history?
It cooled slowly at first and then was ejected from the volcano causing it to cool rapidly.
Describe the way magmas are produced in subduction zones.
Magma upwells because of the stretching and plate tectonics. it cools at the surface creating igneous rock.
Why does melting take place beneath the axis of a mid-ocean ridge?
As the asthenosphere rises it undergoes decompression which leads to melting.
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