Exam 1 Flashcards
(115 cards)
1
Q
order of the layers of the earth from the outside in
A
crust, mantle, core
2
Q
how do we know what is inside the earth?
A
direct evidence: deep drilling. indirect evidence: volcanic activity bringing things up, seismic waves
3
Q
what is the moho discontinuity?
A
the boundary between the crust and mantle
4
Q
what is the gutenberg discontinuity?
A
the boundary between the mantle and the core
5
Q
what is the lehman discontinuity?
A
the boundary between the inner and outer core
6
Q
what do the discontinuities in the earth show us seismically?
A
the speed of waves changes so we know the layers are made of different materials
7
Q
what is the outer core made of?
A
liquid iron and nickel
8
Q
what is the inner core made of?
A
solid iron and nickel
9
Q
how are the layers of earth stratified?
A
density, thermal, pressure
10
Q
what is the principle of isostacy?
A
as heavier things accumulate on the crust, it sinks down. as things erode on the crust it rises.
11
Q
what is it called when the crust rises in the principle of isostacy?
A
isostatic rebound. ex: glaciers
12
Q
what is the earth made of?
A
46.6% oxygen, 27.7% silicon and silicates
13
Q
what are minerals?
A
the building blocks of rocks. ex: mica, feldspar, halite, precious gemstones
14
Q
what are rocks?
A
combinations of minerals
15
Q
how do igneous rocks form?
A
from molten magma
16
Q
how do extrusive igneous rocks form?
A
the magma solidifies above the surface
17
Q
how do intrusive igneous rocks form?
A
magma solidifies in the earth’s crust. they get to the surface via uplift and mountain building
18
Q
examples of extrusive igneous rocks
A
basalt
19
Q
examples of intrusive igneous rocks
A
granite, gabbro
20
Q
what is mafic rock chemistry?
A
when the rock magma originates in the mantle
21
Q
what is felsic rock chemistry?
A
when the rock magma originates in the crust
22
Q
characteristics of mafic rocks
A
low quartz, high magnesium and iron, dark color, high melting temp, low resistance to weathering
23
Q
characteristics of felsic rocks
A
high quartz, high potassium and sodium, light color, low melting temp, high resistance to weathering
24
Q
what are sedimentary rocks?
A
rocks that form from the cementing and hardening of sediments derived from other rocks
25
how do sedimentary rocks form?
1) weathering of pre-existing rocks makes sediment 2) erosion transports sediments by wind, water, ice 3) the material is deposited somewhere 4) the grains of sediment are cemented together via lithification
26
examples of sedimentary rocks
sandstone, shale, limestone (stratified appearance)
27
what are clastic sedimentary rocks?
made up of discrete particles
28
what are non-clastic sedimentary rocks?
made up of chemical precipitates
29
is oceanic crust or continental crust thicker?
continental crust. 50-60 miles vs 7 miles deep.
30
what are metamorphic rocks?
rocks that form when pre-existing rock is subjected to high heat and pressure
31
examples of metamorphic rocks
marble, gneiss, slate, schist
32
what are regional metamorphic rocks?
they form deep in the crust with heat and pressure
33
what are contact metamorphic rocks?
they form from contact with magma
34
how are the boundaries of geologic time determined?
by the organisms found and lost in a certain time
35
who was James Ussher?
he determined the age of the earth via bible references and gave rise to catastrophism.
36
what is catastrophism?
the theory that the earth's crust was formed by ancient catastrophes (volcanos, meteors, etc.) before 4004 BC
37
what are phaneritic rocks?
rocks with large, visible crystals that cooled slowly
38
what are aphantic rocks?
rocks with almost invisible crystals that cooled quickly
39
what are porphyritic rocks?
rocks with some visible crystals in a fine-grain matrix
40
what is the asthenosphere?
the plastic mantle
41
what is the lithosphere?
crust + rigid mantle
42
what is the difference between primary and secondary waves in seismology?
s waves don't pass through liquids and p waves do
43
what are common crust elements?
oxygen, silicon, aluminum, iron
44
what are granite, basalt, and rhyolite examples of?
these are all igneous rocks (intrusive, extrusive, extrusive with high silica)
45
what are obsidian and pumice examples of?
extrusive igneous rocks (one with silica and one with air bubbles)
46
what is vesicular basalt an example of?
extrusive basalt with lots of trapped gas bubbles
47
what is geologic time and how is it shown?
the timeframe of the history of the earth, represented in a vertical column with many rows for periods
48
what was the quaternary period?
this contains the Pleistocene and Holocene periods
49
what was the pleistocene period?
2.6 million years ago to 11,700 years ago, the ice ages
50
what was the holocene period?
11,700 years ago until now, the most recent interglacial period
51
what is geochronology?
dating the earth and earthen events
52
what is relative dating?
putting events into their proper chronological order, doesn't establish an actual age
53
what is absolute dating?
putting an absolute age on an event or geologic phenomenon
54
what is dendrochronology?
dating events via growth rings in trees
55
what is the law of superposition?
sediments at the bottom are older than the top
56
what is original horizontality?
sediments are originally deposited horizontally
57
who was Nicolaus Steno?
1600s man who found shark teeth in rocks and created the law of superposition and the law of original horizontality
58
what is uniformitarianism?
the same processes operating today have operated in the past
59
who was James Hutton?
the founder of modern geology who came up with the theory of uniformitarianism
60
who was Charles Lyell?
he wrote Principles of Geology and helped establish uniformitarianism
61
what are cross-cutting relationships?
when a younger geologic feature cuts across an older feature
62
who was William Smith?
came up with the theory of faunal succession. he built canals so he saw what order fossils were found in
63
what is radiometric dating?
using the decay rates and half-lives of radioactive elements
64
what is K-Ar dating?
based on the amount of decay present from K turning to Ar. good for things older than 70,000 years
65
what is carbon 14/radiocarbon dating?
dating by measuring the decay of Carbon-14
66
what is radiocarbon dating?
when carbon gets cycled into your body and then the clock starts when you die. the c12:c14 ratio changes over time
67
what is a half-life?
the time after which half of an element has decayed
68
what is the theory of plate tectonics?
the lithosphere is broken into plates that move around
69
what is the evidence for plate tectonics?
fossil map of where things are found, matching dinosaur tracks in Africa and South America, matching coastal geologic features, matching chemistry of lava flows, glacier direction on Pangaea going from inner to outer
70
who came up with the theory of continental drift?
Alfred Wegener
71
who was Alfred Wegener?
a German geophysicist and meteorologist who published a horrible book on continental drift
72
what is continental drift?
that the continents started as Pangaea and have moved over time
73
what is pangaea?
super continent
74
who was Marie Tharp?
she created the first map of the sea floor with Bruce Heezen
75
how are midocean ridges formed?
at divergent plate boundaries when two plates are pulling away from each other
76
how are midocean trenches formed?
at convergent plate boundaries where an oceanic plate is being subducted
77
who was Bernard Bruhnes?
he realized that some older basalt samples had the magnetic needle facing South
78
what is paleomagnetism?
the history of magnetic fields
79
what are magnetic reversals?
when the polarity of earth changes
80
what is the epicenter of an earthquake?
the point on earth's surface directly above the focus
81
what is the focus of an earthquake?
where movement on a fault originates. shallow is more violent and close to the surface. deep is less violent and often found in ocean trenches
82
how are earthquakes distributed?
mostly on fault lines
83
how are granite-cored mountain ranges formed?
through uplift and erosion
84
how are volcanic mountain ranges formed?
through magma coming up through the crust and building layers
85
how are marine sedimentary rock mountain ranges formed?
marine sediments between two continental plates are squeezed upwards to form mountain ranges
86
what type of mountain range is the Sierra Nevadas?
granite-cored
87
what type of mountain range is the Cascades?
volcanic
88
what type of mountain range is the Himalayas?
marine sediment
89
who was Harry Hess?
came up with seafloor spreading, the mechanism for continental drift
90
what is seafloor spreading?
new (basalt from the mantle) crust is being formed as the plates of the sea pull apart
91
what is Iceland made of and located on?
basalt volcanos on the mid atlantic ridge
92
who were Vine and Matthews?
they tested the seafloor spreading hypothesis by looking at the patterns of basalt magnetism fond on either side of a rift
93
what are magnetic stripes?
the mirror reflections of the magnetism changing across sea floor rifts
94
what is subduction?
when one plate is pushed beneath another plate into the earth's crust
95
which plate is subducted?
oceanic or denser/older plate
96
how does subduction lead to orogeny?
as the older crust is subducted into an ocean trench, it uplifts the other side
97
what are convergent plate boundaries?
where two plates are colliding head-on
98
what happens at oceanic - oceanic boundaries?
they produce volcanic island arcs because the subducted plate melts to form the magma
99
what happens at oceanic - continental boundaries?
they make granite-cored mountain ranges if the magma solidifies in the crust and felsic volcanic mountain ranges if the magma reaches the surface and cools
100
what happens at continental - continental boundaries?
these are often metamorphic rock that forms marine sediment mountains
101
what are island arc volcanos?
formed by ocean:ocean subduction
102
what are the Aleutian Islands?
island arc volcanos
103
what are suture zones?
a region where two tectonic plates are converging and suturing together
104
what are magma hot spots?
little pockets of magma in the crust that make it up to the surface
105
how were the Hawaiian islands formed?
magma hotspots
106
what is the Loihi seamount?
the newest Hawaiian island that is going to form!
107
why is there a sharp angle in the middle of the Hawaiian islands?
the North American plate slammed into the Pacific plate and changed the direction of movement (hotspot stays in the same place)
108
what are Hawaiian-type shield volcanos?
very flat volcanoes formed with non-viscous lava
109
what are stratovolcanos?
stratovolcanos
110
what kind of magma forms shield volcanos?
non-viscous, basaltic/mafic magma
111
what kind of magma forms the other type of volcanos?
viscous, felsic magma
112
what is an effusive eruption/fissure?
felsic magma erupting with lots of gas to make big explosions
113
what magma is low viscosity and high temperature?
mafic
114
who was Georges Curvier?
he was a French zoologist who looked at fossils and thought they could be older relatives/extinct relatives of animals we currently have on earth.
115
what are index fossils?
fossils with a widespread distribution, found during specific geologic times
