100 terms

mid term

Why do the planets appear to move with respect to the stars?
-stars in the sky remained fixed relative to each other while the entire star field moves slowly around a fixed point.
- A planet does move on its own and does not follow the star field.
Contrast the geocentric and heliocentirc universe concepts.
Geocentric- Earth is motionless at the center of the universe with all other planets revolving around it.
Heliocentric- All planets including Earth revolve around the sun.
Describe how Foucault's pendulum demonstrates that the earth is rotatiing on its axis.
-As a pendulum swings the plane on which it oscillates rotates around a vertical axis.
How did Eratosthenes calculate the circumference of the Earth?
Measured the distance between alexandria and syene which represented 7.2 degress/ 360 degrees of the earths circumference.
What are light years a measure of?
Light years are a unit of distance, the distance light travels in one earth year.
Describe the Doppler effect
Sound emitting from a stationary source has the same wavelength. However, if the source is moviing towards a person, the wavelengths gets smaller(blue/higher) and if it moves away the wavelengths get longer(red/longer)
What does the red shift of the galaxies tell us about their motion with respect to the earth?
That all the planets are moving away from the earth.
Describe the steps in the formation of the universe and the solar system.
The universe started in the cataclysmic explosion, and then gravity began to form the solar system. As each mass became denser, they exploded into supernovas releasing elements and gravity once again began collecting matter together to create planets.
How is a supernova different from a normal star?
-A supernova is short lived very bright object in space that results in the cataclysmic explosion of the death of a large star. Usually contained smaller elements on the periodic table
-Stars are long lived bright objects in space that burn larger elements.
why do the inner planets consist mostly of rock and metal, but the outer planets mostly of gas?
The sun stellar winds blew away the gases on the inner planets but did not reach the outer ones.
Why are all the planets in the solar system orbiting the sun in the same direction and in the same plane.
Since the formation of the planets is centered around the suns gravitational pull, all planets developed the same way, from the crashing of the planetsimals to the same path of orbit.
Chapter 2
Why do astronomers consider the space between planets to be a vaccum, 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 leve is bursting with matter.
What is the Earth's magnetic field?
-Earth has a dipole magnetic field.
-The magentic field exits the bottom of the earth and forms a circle connecting to the top with each layer getting farther and weaker away from the earth.
How does the magentic field interact with solar wind?
The magnetosphere deflects solar winds, then Van Allen stop deadly cosmic radiation and the ions that escaped get pulled to the poles creating the aurorae.
What is the Earths atmosphere composed of, and how does it differ from venus and mercury?
-78% nitrogen, 21% oxygen, 1% other.
-Venus- Carbon dioxide
-mercury- High temperature destroyed the atmosphere.
What is the proportion of land area to sea area on earth?
70% water, 30% oxygen, Roughly 3%
Silicate rocks?
-Iron and oxygen, organic- carbon containing compunds, minerals, and solid substances with uniform atoms.
-glasses- solid with atoms not arranged uniformly.
-rocks- aggregates of mineral crystals or grains.
-metal- Solids composed of metal atom.
-melts- solid material that become hot and turn to liquid.
-volatiles- material that easily transforms into gas at low temps.
How did researchers first obtain a realistic estimate of Earth's average denstiy?
-The average earth density is greater than the surface density.
-Earths shape is a rotating sphere and requires a centered mass.
-Seismic waves penetrate earth, changing the wavelenghts means different density. pressure/temp increases woth depth due to overlaying rocks.
What are earthquake waves?
Ground shaking due to teh sudden bvreakingg of rocks in the Earth.
-Seismic waves are the energy of the vibration.
Does the velocity at which an earthquake wave travels change or stay constant as the wave passes through the earth?
The seismic waves travel at different velocities through different material and depths.
what are the principal layers of the earth?
Crust, mantle, core.
What happens to earthquake waves when they reach the boundary between layers?
The seismic wavelength changes between layers.
How do temperature and pressure change with increasing depth in the earth?
at-Temperature and pressure increase with increasing depth.
-the downward pressure of the earth crams matter together creating heat and as the pressure increases the matter also increases in temperature.
What is a moho?
the change between the crust and mantle.
- and it was recognized because of the changes in the seismic waves.
Differences between continental crust and oceanic crust?
-continental crust is less dense and floats.
-oceanic crust is more dense and floats lower.
what percentage of the earths diameter is within the crust?
0.1% to 1%
what is the mantle composed of?
-consist of ultramafic rock called periodotile.
3 sublayers within the mantle
-Upper mantle
-Lower mantle
-Transition zone
Is there any melt within the mantle?
-No melt
-it has solid rock.
What is the core composed of?
Iron rich sphere.
How do the inner and outer core differ from eachother?
-outer is solid
-inner is liquid
Difference between lithosphere and asthenosphere?
-Lithosphere is the outermost part of earth rigid tectonic plates.
-Asthenosphere is the upper mantle below lithoshpere and it flows as a soft solid.
chapter 3
Wegener's continental drift hypothesis?
Proposed that continents had once been joined together to form a single huge super continent and had drifted apart.
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 occured during the Paleozoic.
Permian glacial till found on 5 continents and now the tills in Africa and india are near the 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 dinosaurs to walk from New York to Paris when pangaea existed?
Yes all the continents were connected at the time, same fossils were found in different countries.
Why were geologists initially skeptical of Wegener's hypothesis?
There was not a force strong enough to move the conitnents.
How could the paleomagnetic inclination be used to determine the ancient latitude of a continent?
The magentized rock is preserved over millions of years so as the continents shift, the direction of magnetic north is preserved in the rock is differ from where the rock is found now.
Basic characteristic 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.
Sea floor spreading
The gradual widening of an ocean basin as new oceanic crust forms at mid ocean ridge axis and then moves away from the axis.
How did the observations of heat flow and seismicity support the hypothesis of sea floor spreading?
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?
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 times lines of the magnetic reversals
What is a marine magnetic anomaly?
Alternating polarity bands of seafloor gathered by magnometers behind boats.
Describe the pattern of marine magnetic anomalies across the mid ocean ridge.
The pattern is symmetrical because the sea floor spread away from the mid ocean ridge.
How did geologists calculate rates of sea floor spreading?
They used global positioning satellites.
Did drilling into the sea floor contribute further proof of sea floor spreading?
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.
chapter 4
characteristics of a lithosphere plate?
Made of both crust and upper mantle, bends elastically when loaded.
how does the oceanic crust differ from continental crust?
Oceanic crust has a basaltic crust, its more dense floats lower. Continental crust has a granite crust, less dense floats higher, so it is more buoyant.
Contrast active and passive margins.
Margins near plate boundaries are active, margins away from the plate boundaries are passive.
What are the basic premises of plate tectonics?
The lithosphere is made up of 15 to 20 plates that move relative to each other and relative to underlying asthenosphere.
How do we identify a plate boundary?
By the breaks in a plate.
describe the three types of plate boundaries.
-Divergent- tectonic plates move apart.
-convergent- tectonic plates move together.
-transform- tectonic plates slide sideways.
how does crust form along a mid ocean ridge?
Seafloor spreading causes plates to move apart, magma wells up to fill the gap, magma cools adding material to each plate.
what happens to mantle beneath the mid ocean ridge?
the mantle cools and becomes part of the lithosphere.
Why are mid ocean ridges high?
Mid ocean ridges are warmer rocks which is less dense than the colder mid ocean ridges are higher because of the warmer rock temperature and areas around it are lower because of the colder denser temperature
why is subduction necessary on a non expanding earth with spreading ridges?
subduction recycles oceanic lithosphere.
what is a Wadati Benioff zone?
A belt of earthquakes that mark frictional contact and mineral transformation between subducting plates.
features of convergent boundary?
Accretionary prism- deformed sediment wedges
volcanic arcs- volcanic belts on an overriding plate.
Back arc basin- Marginal sea behind an arc.
2 examples of famous transform faults?
- San Andreas
- Alpine Fault
triple junction
Place where three plate boundaries coincide.
How a hot spot track is produced?
Volcanic plumes erupt on the surface as the plate shifts the volcanoes goes extinct and tattoo the ocean with small islands.
Continental rift
Continental lithosphere that stretches thin and break apart. this is occurring in east africa.
Continental collision
When two plates collide and the ocean basin is swallowed and mountains are smashed upwards.
Major forces that move lithospere plates.
-Ridge push- elevated MOR pushes adjacent lithosphere
-Slab pull- gravity pulls a subducting plate downward.
Can we measure present-day plate motions directly?
Yes, plotting plate motion relative to a fixed spot in the mantke or by measuring volcanoes ages/distances along a hot spot track.
chapter 5
what is a mineral as geologist understand the term?
Naturally occurring solid inorganic crystalline and definite chemical composition. minerals are usually refered to as all the above except for atoms.
why is glass not a mineral?
glass is not a crystalline because its atoms are not orderly arranged.
why is the plastic of a pen not a mineral?
A pen is not a naturally occurring mineral.
the differences between diamond and graphite in terms of their crystal structure.
Diamond- Tetrahedron, covalent bonds.
Graphite- sleet bonds they are polymorphs, have different crystal structures.
Ways that mineral crystals can form?
Euhedral- well formed faces uninhibited growth.
-Anhedral- non well formed inhibited growth.
physical properties used to identify a mineral.
Color, streak- color of a mineral. crushed onto porcelain.
luster- shine.
hardness- scratching resistance.
specific gravity- mass per volume.
crystal habit- shape of the crystal.
cleavage- crystal that breaks in a predetermined place.
Fracture- curving surfacecs that break without cleavage.
Chemical formula od Quartz, halite, and calcite.
-Quartz- SiO2
-Halite- NaCl
-Calcite- CaCO3
what holds atoms together in a mineral?
chemical bonds.
how can you determine the hardness?
If it can scratch or becomes scratch from another mineral.
Mohs hardness scale
the scale of hardness from 1 to 10.
prime characteristic that geologists use to separate minerals into classes?
their dominant anion.
What is the principal anionic group?
SI- 4 silicon atom with 4 oxygem atoms in a tetrahedron.
Relationship between silicon oxygen tetrahedra bond in micas and cleavage of micas.
it is a 2 dimensional sheet of linked tetrahedral characterized by one direction of perfect cleavage.
how does sulfate differ from sulfide?
-Sulfates- cation produced by sulfate.
-Sulfide- cation produced by sulfide.
why are some minerals considered gems?
because they are cut and polished crystals used in jewelry facets.
how do u make the facet on a gem?
made by a machine.
chapter 6
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.
what is the source of heat in the earth?
Heat comes from gravitational compression, differentiation, radioactive decay.
how did the first igneous rocks on the planet form?
Magma was heated to extreme temperatures either in earth or above and solidified.
3 processes responsible for the formation of magmas.
-Partial melting from pressure release
-volatile addition
-heat transfer
why are there so many different types of magmas?
because of the different percentages of silica partial melting, assimilation, magma mixing, fractional crystallization.
Why does magma 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- more 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
describe the way magma are produced in subduction zone.
Magma upwells because of the stretching and plate tectonics. it cools at the surface creating igneous rock.
Large igneous provinces
places with huge eruptions of igenous rock.
How might the formations affect the earth system?
the formation and change of landscape affect the seawater and life on earth.
why does melting take place beneath the axis of a mid ocean ridge?
As the asthenosphere rises it undergoes decompression which leads to melting.