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199 Cards in this Set
- Front
- Back
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Galaxy |
a collection of stars (immense balls of gas that emit incredible heat and light) held together by gravity |
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Moon |
a sizeable spherical body locked in orbit around a planet |
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Asteroid |
chunk of rock or metal |
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Comet |
icy objects that form a gaseous tail when approaching the sun |
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The Big Bang |
all matter and energy in the universe was once packed into an infinitesimally small point that exploded 13.7 billion years ago. The universe has been expanding ever since |
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The Doppler Effect |
the frequency of a wave changes as the source of the wave moves. Energy (sound, light) travels as waves |
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Wavelength |
distance between wave crests |
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Frequency |
number of waves that pass a point in a given time interval |
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Blue Shift |
the principle of light energy where blue light indicates short wavelength, high frequency light- objects moving towards you |
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Red Shift |
the principle of light energy where red light indicates long wavelength, low frequency light- objects moving away from you |
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What elements formed in the big bang? |
hydrogen, helium, and lithium |
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What elements combined inside the stars to form heavier elements (nuclear fusion) from Beryllium through Iron? |
Hydrogen and helium |
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What elements formed in exploding stars (supernovae)? |
cobalt through uranium |
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Nebular theory of planet formation |
planets formed from the material (dust and gas) surrounding a new star. Gravitational forces and collision slowly combine the “dust bunnies” of the protoplanetary disk into actual planets. |
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Differentiation |
Bigger planets were hot enough for the interiors to melt, causing dense materials (like iron alloy) to sink to the center and light materials (rocks) to form shells on the exterior (think of egg analogy) |
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Formation of the Moon |
Earth collided with a Mars-sized planetary body~4.5 Ga (billion years ago) , and the resulting ring of debris eventual coalescedinto the moon |
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Basic structure and composition of the earth |
Mostly Silicate rocks (silicon + oxygen) surrounding an iron core |
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Radius of the Earth |
6371 km |
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Deepest hole ever drilled |
12 km(Kola Borehole, Russia) |
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Peridotite |
a coarse-grained ultramafic rock |
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Mantle Xenoliths |
clasts of mantle rocks entrained within magmas, providing samples of Earth's upper mantle. The majority are periodotites |
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Clast |
a fragment or grain produced by the physical or chemical weathering of preexisting rock |
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Fault |
a fracture on which one body of rock slides past another |
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What indicated the presence of distinct layers of earth within different composition? |
When rock breaks and slips,forming a fault, it generates shock waves that pass through the Earth and shake the surface. These shock waves were observed to travel through the Earth atvariable speeds |
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Crust |
The rock that makes up the outermost layer of the Earth |
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Composition of Continental Crust |
thicker than oceanic crust (35-40 km);variable rock type, but generally less dense |
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Composition of Oceanic Crust |
thin (7-10 km), made of dense rock (basalt, gabbro) |
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Basalt |
a fine-grained, mafic igneous rock |
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Gabbro |
a coarse-grained, intrusive, mafic igneous rock |
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Mafic |
a term used in reference to magmas or igneous rocks that are relatively poor in silica and rich in iron and magnesium |
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Ga (abbreviation) |
Billions of years |
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ultramafic |
a term used to describe igneous rocks or magmas that are rich in iron and magnesium and very poor in silica |
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Moho |
The boundary between the crust and the mantle where the chemical composition of the rock changes (named for its discoverer, Mohorovičić) |
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Mantle |
The thick layer of rock below the Earth's crust and above the core. Made entirely of the rock peridotite; split into upper and lower mantle. |
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Lithosphere |
The relatively rigid, nonflowable, outer 100- to 150-m thick layer of the Earth, constituting the crust and the top part of the mantle. rigid, brittle shell; crust + uppermost mantle |
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Core |
The dense, iron-rich center of the Earth. "Earth’s metal yolk." Outer core – liquidiron alloy /// Inner core – highpressure forms verydense, solid iron alloy |
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Asthenosphere |
(1) The layer of the mantle that lies between 100-150km and 350 km deep; it is relatively soft and can flow when acted upon by force. (2) plastic region of the mantle where temperaturesare hot enough (1280°C) to allow rock to flow |
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Are gas molecules more closely packed together nearer or further from the earth? |
Nearer |
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Magnetosphere |
The region protected from the electrically charged particles of the solar winds by Earth's magnetic field. Earth acts like a giant dipole magnet (N and S poles) that generates amagnetic field around the planet |
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Polarity of the Magnetic Poles |
North Magnetic Pole-- Southern polarity South Magnetic Pole-- Northern polarity |
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Magnetic field |
The region affected by the force emanating from a magnet. Earth acts as a magnetic dipole and generates a magnetic field due to circulation of liquid iron in the outer ore. |
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What cause gases in the atmosphere to glow (i.e. the Northern Lights?) |
Charged particles in the atmosphere flowing toward Earth’s magnetic poles |
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Do seismic waves travel at the same velocity throughout the Earth? Why? |
No. The velocity changes with depth, and at certain depths the change is abrupt |
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Nuclear Fusion |
The process of hydrogen and Helium inside the stars combined to form heavier elements, from Beryllium through Iron |
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Supernovae |
Exploding stars; a short-lived, very bright object in space that results from the cataclysmic explosion marking the death of a very large star; the explosion ejects large quantities of matter into space to form new nebulae |
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What elements formed during the big bang? |
hydrogen, helium, and lithium |
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Atoms that are heavier than iron are generally produced by... |
explosions of supernovae |
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Heliocentric Model |
Claims the sun is at the center of the universe and all objects revolve around it. Popularized in the Renaissance by Copernicus and Galileo. |
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Geocentric Model |
Earth is at the center of the universe and all objects revolve around it. Popular from 100-1400 A.D. |
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The key evidence that the Universe is expanding is... |
the red shift of light from distant galaxies (discovered by Edwin Hubble) |
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Is the metal alloy that makes up the core of Earth more or less dense, as compared to the rocky mantle? |
More dense |
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Presently, Earth’s atmosphere is dominated by which two gases? |
nitrogen and oxygen |
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Does pressure, like temperature, increase as you get closer to the center of the earth? |
Yes |
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Earth’s magnetic field is generated by... |
convection currents in the liquid outer core |
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The Principle of Uniformitarianism |
States the physical processes we observe today also operated in the past in the same way, at comparable rates. Proposed by James Hutton in 1795. |
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Formation of continental crust |
Continental crust formed from mafic igneous rocks that originally extruded or intruded at convergent plate boundaries and/or hot-spot volcanoes. Once formed, these rocks were too buoyant to be subducted, so when the arcs and plateaus collided with one another, they structured together to form larger blocks that remained at the earth's surface. The development of convergent plate boundaries along the margins of these blocks, and of rifts and hot spots within the blocks, led to production of flood basalts. Partial melting of basaltic crust yielded felsic and intermediate rocks. As collisions continued, the blocks coalesced into larger proto-continents, which slowly cooled and became stronger. As a result of these processes, the first long-lived blocks of durable continental crust came into existence, and by the end of the Archean Eon, about 80% of the continental area had formed. |
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The largest intervals of geologic time |
Eons |
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Eras of the Phanerozoic Eon |
1) Paleozoic (542 to 251 Ma) 2) Mesozoic (251 to 65.5 Ma) 3) Cenozoic (6.5 Ma to present) |
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Cenozoic Era |
--The most recent era of the Phanerozoic Eon --“Recent life” --65.5 Ma to present --The “Age of Mammals” |
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Paleozoic Era |
--The oldest era of the Phanerozoic Eon -- “Ancient Life” --542 to 251 Ma --Life diversified rapidly --Continents Reassemble, and Life Gets Complex |
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Mesozoic Era |
--The middle of the three Phanerozoic Eras -- “Middle Life” --251 to 65.5 Ma --The “Age of Dinosaurs” |
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The fossil record indicates that complex, multicellular animals (e.g., worms and jellyfish)appeared... |
in the late Proterozoic (i.e., about 700 Ma). |
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Huge coal swamps covered inland areas of continents during the _______ . |
Late Proterozoic era |
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Approximate age of the Earth |
4.57 billion years old! |
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Hadean Eon |
--A.K.A. "Hell" --(4.6 to 4.0 Ga) --The earth separated into core, mantle, and crust (internal differentiation) --The moon formed --No rock record exists due to magma oceans and constant bombardment of planets --Formation of the oceans and secondary atmosphere |
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How are eons and eras separated? |
By observed major changes in the rock record (for example, extinction events) |
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Phanerozoic Eon |
-- “Visible life” --542 Ma to the present) --Started 542 Ma at the Precambrian / Cambrian boundary --1st appearance of hard shells; life diversified rapidly afterwards |
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Proterozoic Eon |
--“Early life” --(2.5 to 0.542 Ga) --Development of tectonic plates like today --Buildup of atmospheric O2; multicellular life appears |
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Archean Eon |
“Ancient” --(4.0 to 2.5 Ga) --Birth of continents --Appearance of the earliest life forms |
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Precambrian Time |
The interval of geologic time between Earth's formation about 5.57 Ga and the beginning of the Phanerozoic Eon 542 Ma. Comprised of the Hadean, Archean, and Proterozoic Eons. |
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Cambrian explosion of life |
The remarkable diversification of life, indicated by the fossil record, that occurred at the beginning of the Cambrian Period. |
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Ma (abbreviation) |
Millions of years |
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When was nearly all continental crust formed? |
during the Archean to mid-Proterozoic |
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Early crust formed from... |
the collision and suturing together of volcanic rock bodies |
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Which gas found in today’s atmosphere was nearly absent in the Hadean Eon? |
Oxygen |
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The earliest forests containing woody trees appeared during the __________. |
Middle Paleozoic (Devonian) |
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The fossil fish Tiktaalik is noteworthy because it... |
represents a transitional form between fish and land creatures |
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Rodinia |
(1 – 0.7 Ga) --A proposed Precambrian supercontinent that existed around a billion years ago. --Collisions brought most of the continental crust together into one giant continent that eventually broke up into separate smaller continents |
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According to Wegener’s hypothesis of continental drift, all continents were once attached and formed a single land mass that he called ________ . He thought that this land mass survived until about the middle of the _________ Era. |
Pangea/Mesozoic |
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What is the relationship between the coastlines on the east side of the Atlantic and those onthe west side? |
Continents on the east side could fit snugly against those on the west. |
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Archean Atmosphere |
--As Earth cooled, water vapor in the atmosphere became liquid and filled the ocean basins --Carbon dioxide from the atmosphere dissolved into the oceans(carbonation) --Nitrogen (N2) wasleft behind! --No oxygen ... yet |
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Stromatolites |
Layered mounds of sediment formed by cyanobacteria; layers are built as sediment sticks to mucous secreted by the cyanobacteria |
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Expanding Universe Theory |
Edward Hubble looked to the sky and saw that light from all the galaxies were red-shifted – that is, moving away from us. |
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Nebulae |
Swirling gas clouds |
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Atom Formation |
Only the elements hydrogen, helium, and lithium formed in the Big Bang. Hydrogenand Helium inside the stars combined to form heavier elements (nuclear fusion) from Beryllium through Iron. Cobalt through Uranium formed in exploding stars (supernovae). |
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Birth of Stars |
Formed from the gravitational collapse of swirling gas clouds (nebulae). |
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protoplanetary disk |
a rotating circumstellar disk of dense gas surrounding a young, newly-formed star. |
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protoplanet |
A body that grows by the accumulation of planetesimals but has not yet become big enough to be called a planet |
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terrestrial planets |
Planets that are of comparable size and character to the Earth and consist of a metallic core surrounded by a rock mantle. Put more simply, planets composed of solid material |
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Gas Giants |
Planets composed of gas |
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Are gas molecules more closely packed together further away from the earth's surface, or nearer? |
Nearer |
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Seismic Waves |
Waves of energy that travel through the Earth's layers, and are a result of an earthquake,explosion, or a volcano
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What two qualities help decide whether an object is melted or solidified? |
Pressure and temperature |
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carbonation |
Carbon dioxide from theatmosphere dissolved into the oceans during the Archean |
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Black Smokers |
Hostile vents on the ocean floor which support a deep sea ecosystem. During the Archean, they spewed outchemical energy that could support single-celled organisms (bacteria and archaea) |
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The Great Oxygenation Event |
During the Proterozoic, photosynthetic organisms began producing oxygen gas (O2) as a wasteproduct. O2 accumulated in the atmosphere. |
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Cratons |
A cold, long-lived block of durable continental crust found in the relatively stable interiro of a continent. Formed by 1 Ga |
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Shield |
areas wherePrecambrian rock is exposed |
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Cratonic platform |
area where Precambrian rock is covered by younger rocks |
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Orogenies |
mountain-building events |
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prokaryotic life |
single-celled organisms with no nucleus |
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eukaryotic life |
cells that have no nuclei |
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Ediacaran fauna |
complex, soft-bodied marine organisms appeared in the late Proterozoic |
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Banded Iron Formations (BIFs) |
Oxygen reacted with dissolved iron in the oceans to form iron oxide minerals – aka “rust” – that accumulated on the ocean floor as Banded Iron Formations (BIFs) |
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What did Earth and life look like in the Cambrian and Ordovician periods of the Paleozoic? |
Continents were periodically flooded with shallow seas due to sea level rise, depositing sediment and fossils. During this time, the Cambrian Explosion occurred. |
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What did Earth and life look like during the Silurian-Devonian Periods of the Paleozoic? |
--More fluctuating sea level and deposition of marine fossils on continents --Vascular plants rooted on land and giant swamps developed --Jawed fish evolved in the oceans --First marine amphibians crawled onto land |
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What did Earth and life look like during the Carboniferous- Permian Periods of the Paleozoic? |
-- Supercontinent Pangea formed --Low sea level due to cooling climate -- Life grew more familiar to what we see today --Ferns, conifer trees grew large and died tocreate large coal swamps, where woodydebris transformed to coal upon burial --Abundant life on land, including insects,amphibians, and reptiles |
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The End Permian Extinction |
95% of marine and 76% terrestrial organisms went extinct |
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Periods of the Paleozoic Era (of the Phanerozoic Eon) |
1) Cambrian 2) Ordovician 3) Silurian 4) Devonian 5) Carboniferous 6) Permian |
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Periods of the Mesozoic Era |
1) Triassic 2) Jurassic 3) Cretaceous |
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What did Earth and life look like during the Mesozoic Era? |
---Supercontinent Pangea began to rift apart to form the continents weknow today, and the Atlantic ocean --Very warm climate --Rise and fall of dinosaurs -- First feathered birds and smallmammals --Modern fish --Angiosperms (flowering plants) developed on land --End marked by rapid mass extinction, likely due to meteorite impact. |
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Angiosperms |
flowering plants |
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The (Cretaceous-Tertiary) K-T boundary event/impact |
During the Mesozoic, 65 million years ago: Meteorite hit Yucatan Peninsula to create 100 km wide Chicxulub crater. Debris ejected into atmosphere and led to perpetual winter |
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Periods of the Cenozoic Era |
1) Paleogene 2) Neogene 3) Quaternary |
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What did/does Earth and life look like during the Cenozoic Era? |
-- Formation of today’s major mountain chains: the Alpine-Himalayan chain (continental collisions) and Andes and Rocky Mountains --Rapid cooling led to continental glaciers that have advanced and retreated multiple times -- “The Age of Mammals” – mammals rapidly diversified in the absence of the dinosaurs --Forests and wide grasslands --Evolution of hominids and eventuallymodern humans (< 200,000 y) |
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Pleistocene Ice Age |
Lasted until ~12,000 years ago and partially covered continent with ice |
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Sea Floor Spreading |
a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. Seafloor spreading helps explain continental drift in the theory of plate tectonics. |
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Plate Tectonics |
The theory that Earth's outer shell is divided into several plates that glide over the mantle (the rocky inner layer above the core). The plates act like a hard and rigid shell compared to Earth's mantle. This strong outer layer is called the lithosphere. |
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Marine magnetic anomalies |
the difference between the expected and actual strength of the magnetic field recorded in the ocean basalt |
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Glacial Till |
unsorted material deposited by glaciers |
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Mid Ocean Ridge |
a 2km high submarine mountain belt that forms along a divergent oceanic plate boundary |
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Evidence of Continental Drift |
1) Fit of continents 2) Past glaciations 3) Climate belts 4) Fossils 5) Geologic units 6) Paleomagnetism 7) Sea floor spreading |
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Evidence of continental drift from the fit of continents |
The continents fit together (observed since 1500s by numerous scholars such as DaVinci, Sir Francis Bacon, Benjamin Franklin). |
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Evidence of continental drift from past glaciations |
Glacial deposits (till) and striations from the Paleozoic era exist all over the world, even in modern tropical climates. |
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Striations |
linear grooves/ scratches cut into bedrock by boulders embedded in a moving glacier |
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Evidence of continental drift from climate belts |
Wegener looked for evidence of tropical and subtropical paleoclimates in Paleozoic rocks across the world – and found it. |
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Evidence of continental drift from fossils |
Wegener thought if all the land masses were together, creatures would have moved freely across all continents (unlike recent past, where evolution diverged on isolated continents like Australia). |
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Evidence of continental drift from geologic units |
Geologic structures, rock types, and rock ages match across continents and fit together in the absence of the Atlantic Ocean |
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Magnetic declination |
the angle between the magnetic pole and the geographic pole-- varies depending on where you are on the earth |
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Paleomagnetism |
the record of ancient magnetism preserved in rock |
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Polar wander |
The phenomenon of the progressive changing through time of the position of the Earth's magnetic pole, relative to a locality X, assuming that the position of X on Earth has been fixed through time (in fact, poles stay fixed while continents move) |
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Bathymetry |
depth variation in the ocean floor |
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Deep ocean trenches |
8-12 km deep troughs that border volcanic arcs (curved chains of activevolcanoes). |
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Fracture zones |
narrow bands of fractured, broken up rock that lie perpendicular to the mid-ocean ridges |
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What did Magnetometers towed behind research vessels reveal? |
that the strength of the magnetic field recorded in ocean basalt was striped and symmetrical on each side of the mid-ocean ridge. Repeated measurements from volcanic rock around the world revealed that all rocks showed similar magnetic anomalies, but in vertical layers. Rock layers from different lava flows show same reversal as basalt on the ocean floor. CONCLUSION: Earth’s magnetic dipole flips back and forth over geologic time scales (magnetic reversals), leading to the anomalies |
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positive anomalies |
form when sea-floor rock has the same polarity as the present magnetic field |
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negative anomalies |
form when the sea-floor rock has polarity that is opposite to the present field |
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Reversals |
Earth’s magnetic dipole flips back and forth over geologic timescales (magnetic reversals),leading to the anomalies |
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Types of plate boundaries |
1) Divergent 2) Convergent 3) Tranform |
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Divergent plate boundaries |
two plates move away from the axis of a midocean ridge, andnew oceanic lithosphere forms. Magma from the mantle rises to the surface at the ridge, solidifies to form ocean crust, then moves laterally away from the ridge. |
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Convergent plate boundaries |
two plates move toward each other – the downgoing plate sinks beneath the overriding plate. Continental crust is too buoyant to sink into the asthenosphere, so it always wins in a battle with denser oceanic lithosphere. |
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Transform boundaries |
two plates slide past each other on a vertical fault surface. |
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Oceanic crust formation |
New oceanic crust is formed at divergent boundaries at mid-ocean ridges. |
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Passive margin |
edge of a continent that is not a plate boundary |
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Active margin |
edge of a continent that is a plate boundary |
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Continental Rifting |
can split a continent in two and form a new ocean basin |
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Actuary Prism |
wedge of rock/sediment scraped off the downgoing plate onto the overriding plate |
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Volcanic Arc |
chain of active volcanoes formed as magma rises from melting of the subducting plate |
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Important features of Subduction Zones |
1) trenches 2) actuary prisms 3) volcanic arcs |
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Volcanic island arc |
form when one oceanic plate subducts beneath another |
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continental volcanic arc |
form when the oceanic plate subducts beneath a continental plate |
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What drives the motion of the plates? |
Heat flow from deep in the Earth generates ridge push and slab pull |
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Slab pull |
Dense subducting slabs sink into the asthenosphere, dragging the plate with it |
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Ridge push |
Gravity causes the elevated lithosphere at the MOR axis to push on the lithosphere that lies further from the axis |
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Hot spots |
volcanic regions thought to be fed by underlying mantle that is anomalously hotcompared with the surrounding mantle. They may be on, near to, or far from tectonic plate boundaries. |
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Mantle plumes |
an upwelling of abnormally hot rock within the Earth's mantle. As the heads of mantleplumes can partly melt when they reach shallow depths, they are thought to be the cause of volcanic centers known as hotspots and probably also to have caused flood basalts. |
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Hot spot tracks |
Remnants of a hotspot as evident from the moving of the lithospheric plates (i.e. Hawaii). The youngest volcano of the track occurs at one end of the track. |
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Seamounts |
underwater mountains that rise hundreds or thousands of feet from the seafloor. |
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Velocity |
The speed of the plates. Thought to be around 2cm a year. |
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Igneous rocks |
Melt (lava and magma) eventually cools and hardens to form igneous rock |
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lava |
melt that has emerged at the Earth’s surface |
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magma |
melt that exists below the Earth’s surface (e.g., in the mantle or inside a volcano) |
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extrusive igneous rocks |
Lava cools quickly as it comes in contact with cold air or water at the Earth’ssurface |
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Intrusive igneous rocks |
Magma cools slowly underground as heat is transferred to surrounding rocks. |
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Nature of Earth's internal heat |
The earth has cooled over time since formation, but still has a lot of internal heat due to decay of radioactive elements. |
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How does magma form? |
In one of three ways: (1) Decompression (2) Flux melting (3) Heat transfer |
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Decompression melting |
Decompression melting occurs when the pressure on a hot rock decreases, moving it from a solid to a liquid state. |
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Flux melting |
Flux melting occurs when chemicals called volatiles mix with hot mantle rock to form magma. |
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Heat Transfer melting |
magma rising up into the crust heats and melts the crustal rock around it |
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Viscosity |
The resistance of material to flow. The speed of magma and lava flow is controlled by viscosity. Depends on temperature, volatile content, and silica content. |
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Factors that affect the rate of magma cooling |
1. Depth of intrusion ( deeper rocks cool more slowly because their environment is warmer) 2. Shape and size of the magma body (blobs of magma with greater surface area cool more quickly) 3. Presence of circulating groundwater (water passing through magma carries heat away from the magma body--like coolant in a car engine) |
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Sill |
a tabular intrusion that injects between layers of rock and may cause uplift |
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Dike |
a tabular intrusion that cuts across layers of rock; fills space that forms when crust is stretched and thinned |
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Laccolith |
a blister-shaped intrusion that forms when magma injects between layers underground in a manner that pushes overlying layers upward to form a dome |
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Pluton |
an irregular or blob-shaped intrusion; can range in size from tens of m across to tens of km across |
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Batholith |
vast collection of numerous plutons that may be several hundred kilometers long (i.e. mt. rushmore) |
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Mafic rocks |
contain a lot of Magnesium and Iron in place of Silicon (typically darker in color) |
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Felsic rocks |
Rocks containing more silicon than mafic rocks; rich in elements forming feldspar and quartz; typically lighter in color |
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What is magma made of? |
*liquid rock --Most rocks are made of silica (SiO2) and other elements --Magma is defined by its silica content (% silica) |
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Flood basalt |
Vast sheets of basalt that spread from a volcanic vent over an extensive surface of land; they may form where a rift develops above a continental hot spot, and where lava is particularly hot and has low viscosity. |
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When Wegener compared rock units now exposed on different continents bordering theAtlantic Ocean, what did he discover? |
Fossils of identical land-dwelling species occur on continents that are now separated from one another by the ocean. |
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Without plate tectonics, we would not have… |
plates in constant motion, the formation of new oceans, and mountain building. |
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Observations of the seafloor indicate that heat flow is greatest… |
among mid-ocean ridges |
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Does the age of oceanic crust increase or decrease with increasing distance from a mid-ocean ridge? |
Increases |
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What two rocks primarily compose oceanic crust? |
Gabbro and basalt |
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Regions of the sea floor with negative magnetic anomalies were formed during times whenEarth’s magnetic field… |
was exceptionally weak |
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Marine magnetic anomalies result from sea-floor spreading in conjunction with... |
magnetic polarity reversals |
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Is the asthenosphere or the lithosphere able to flow over long periods of time? |
The asthenosphere |
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Slab pull occurs because subducting slabs are… |
cooler, and therefore denser, than surrounding asthenosphere |
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The lithosphere of the Earth is generally thinnest at and near what type of plate boundary? |
Divergent |
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If mid-ocean spreading was to stop, but subduction continue, what events would occur? |
Continents would begin moving toward each other, the surface area of the Earth would decrease, and sea levels would rise. |
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Over the entire surface of the earth, is lithospheric production greater than, less than, or equal to lithospheric consumption? |
equal |
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The volcanoes of the Cascades Mountains are related to melting of rock associated with what type of plate boundary? |
convergent |
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Segments of the mid-ocean ridge system are offset. Between the offset segments we observe... |
transform faults |
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What explains the occurrence of marine fossils on Mount Everest? |
the collision between India and Asia uplifted marine sediments |
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Volatiles |
substances that have a tendency to evaporate and are stable as gases |
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Melts refer to... |
lavas and magmas |
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Why can samples of basalt exhibit paleomagnetism? |
The dipoles of tiny magnetite grains in basalt align with the Earth’s field as the basalt cools and stay that way once the basalt is cold. |
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What processes form granite boulders in Joshua Tree National Park? |
cooling of extrusive lava above ground |
