Glaciers, Plate Tectonics Flashcards
1
Q
What are the two major types of glaciers?
A
- Continental
- alpine / valley glacier
2
Q
What are the two rates you have to look at to tell if you a glacier is advancing or retreating?
A
Melt rate and flow rate
3
Q
What are glacial stratiations
A
When a glacier drags a large boulder and leaves scratches on the bedrock
4
Q
What are glacial grooves
A
When the glacier drags a huge boulder and it leaves large grooves
5
Q
What kind of glacier grows primarily in mountains, and are smaller scale
A
alpine/valley glaciers
6
Q
What kind of glaciers are large scale, think Greenland or Antartica?
A
continental glaciers
7
Q
What happens if the melt rate=flow rate for glaciers?
A
Static position, front will not move forward, like going opp way on an escalator, you are always moving forward
8
Q
How do moraines form?
A
If glacier is not moving (melt rate=flow rate), boulder/sand/mud gets deposited at the “front” of the glacier forming an elongated hill made up of the till
9
Q
Anything deposited by a glacier is known as _______.
A
glacial drift
10
Q
Unsorted glacier drift is known as _______
A
till
11
Q
What is a glacial stream?
A
When melt water flows away from the glacier
12
Q
The flat plains that form around a glacial stream that is layered is called?
A
outwash plain
13
Q
Boulders deposited by glaciers tend to be angular/rounded?
A
rounded
14
Q
Boulders deposited by a glacier that is of completelty different type of rock from the bedrock on which it sits is known as a __________
A
glacial erratic
15
Q
When a glacier moves through a valley, it erodes the sides of the valley down making a what kind of shape?
A
U shape
16
Q
Define what a glacial horn is
A
A pyramid like peak formed by glacial action in three or more cirques surrounding a mountain summit
17
Q
Define what a glacial arete is
A
A narrow, knifelike ridge separating two adjacent glaciated valleys
18
Q
What is a cirque
A
A amphitheater shaped basin at the head of a glaciated valley produced by frost wedging and plucking – where the glacier starts
19
Q
How do kettles form?
A
Blocks of ice get stranded and form pockets/low areas that melt. Form as glaciers retreat.
20
Q
_________ refers to the annually laminated sediment deposited at the base of some lakes, or marine settings. These sediments are incredible resources for researchers who look into changes in climate and environmental systems in the past. This is because they can record changes to these systems at an annual, or even seasonal resolution. Because the sediment accumulates in annual layers, it means the chronology of the sediment is robust as you can count back the annual layers, just like an ice core making these sediments much more accurate than other methods of reconstructing past changes.
A
varved lake deposits
21
Q
What do you call the chunk of ice that breaks off from a glacier when it reaches the ocean?
A
icebergs
22
Q
A streamlined symmetrical hill composed of glacial till. The steep side of the hill faces the direction from which the ice advanced.
A
drumlin
23
Q
An asymmetrical knob of bedrock formed when glacial abrasion smooths the gentle slope facing the advancing ice sheet and plucking steepens the opposite side as the ice overrides the knob
A
roche moutonnee
24
Q
What is an esker?
A
melt in bottom of glacier creating a cave that is being filled with sediment. Creates snake like elongated hill that looks like a moraine but has sorting and layers.
25
What are some of the causes of an Ice Age
1. composition change of the atmosphere
2. plate tectonics - position of continents if all at the equator nothing for the ice to climb ontop
3. milankovich cycles
26
What is the first change in the Milankovich cycle?
Change of Earth's orbit shape around the sun. Circular orbit to elliptical. Every 100k years goes through a cycle. Goes from 0.0034 (almost perfect circle) to 0.058 (slightly elliptical)
27
What is the second change in the Milankovich cycle?
obliquity, the earth's tilt on its axis. goes through the cycle every 41k years and the tilt angle goes from 22.1 to 24.5 degrees.
28
What is the third change in the Milankovich cycle?
procession - the wobble on the axis will affect the increase and decrease in solar radiation. every 26k years go through this cycle
29
What is the Moho boundary?
The line between the crust and the mantle
30
How thick is the continental crust? Oceanic crust?
Continental 30-40km, oceanic 5km
31
Which of the earth’s layers contain silicas?
Crust and mantle
32
Where is the lithosphere?
Crust & Upper mantle, 100km down, rigid
33
Where is asthenosphere? Describe some properties of it
200km down in the mantle. Plastic and semi molten
34
What is the area of the mantle under the asthenosphere called?
Transition zone. As you go down more heat and pressure. Olivine will rearrange your form periovoscite which will change to something else in a step wise fashion. Ends at 700km down. Once below 700km no obvious changes occur.
35
How do we know the earth has layers?
Indirect evidence…
1. Earth has magnetic field. Electrons that move around which usually happens when you have a strong metal moving around. (Evidence for iron rich core) dynamo effect. Moon doesn’t have bc it’s frozen.
2. Earthquakes - studying p waves and S waves and how they refract
3. Meteorites - stony, stony irons and iron
4. Density calculations - 2 independent ways of calculating density of the earth match, Newton law of gravity and our model.
5. Ophiolite sequence - sequence of rocks we see at surface layer periodotite, layer basaltic, layer sed marine rocks (not common)
6. Xenoliths - exotic blocks of minerals in intrusions that will be exposed in weathering.
36
Which of the two earthquake waves don’t travel thru liquid?
S waves.
37
Briefly describe how s and p waves move
P is primary and compressive. Cause particals to come together and pull apart. Will travel thru solids and liquids. Move faster
S is secondary and translational, up and down and back and forth. Also called shear waves.
38
The further apart the waves are the closer/further you are from the epicenter.
Further
39
In which density do the waves move faster? Higher or lower?
Move faster in higher density.
40
What happens to a wave when it does thru high density area to low density area?
The wave gets bent away from boundary — refracted.
41
Where is the S wave shadow zone from epicenter?
From 105-105 degrees
42
Where is p wave shadow zone and why does it do that?
105-142 and it’s because the core is making it be refracted.
43
For our density calculations for the Earth — how do we get the mass?
We know the composition of the Earth, and how big it is, so we can figure out the combined mass from the composition.
44
What is the calculation to find the volume of the Earth
V (earth) = 4/3 pi r^3
45
What is the equation for Newton’s Law of Gravity
F = (GMm)/r^2
G - gravitational constant
M - mass of earth
46
What is the average density of the earth?
5.5 g/cm^3
47
Usually the Ophilite Sequence is above/below granite rock.
Above.
48
What is the name of the model of the earth’s continents before continental drift was a thing?
“Fixed Continent Model”
49
How long ago did Pangea begin to break apart?
200 Mya
50
What is the evidence for continental drift?
1. Jigsaw puzzle fit of continents
2. Mountain ranges/rock sequences match across the Atlantic
3. Fossil data matched in areas across the Atlantic
4. Paleoclimate - glaciers & coal deposits
51
What was some specific evidence for the fossil evidence made by Wegener.
fossil Lystrasaurus - 240mya, only found in S Africa, India, Antarctica. Not a good swimmer, so wouldn’t swim across ocean. But these plates would be touching in his Pangea.
Fossil Mesosaurus - only found in Eastern S America, Western S Africa. Webbed feet but only found in lake deposits
52
What was the argument about glaciers Wegener was making to support Pangea.
Glacial deposits look like coming from the ocean inland, but that would go against gravity. When you put Pangea together, Africa was the center of the glacier and it moved out form there
53
What was the argument Wegener was making about coal deposits to support Pangea.
Coal is the accusation of dying plants, you get fossils of plants in coal deposits. Pangea age deposits were found in high latitudes. You also found tree fossils that didn’t have any rings, the trees found without rings are only found in tropical areas (where there is no differential growth to form rings, seasons). So how are they in high latitudes with seasons?
54
What was a weakness in Wegener’s argument about Pangea that he didn’t know how to answer?
What caused the movement of plates?
55
How did Hess contribute to the discoveries of sea floor spreading?
used a ship with a sonar to map sea floor, see how deep it was.
56
How did Marie Thorp and Bruce Hegel contribute to the discoveries of sea floor spreading?
Found existence of MORs - mid ocean ridges. Also these look like the East African rift zone, tension pulling across crust lots of volcanos and earthquakes. Plotted earthquakes and found they were common along these ridges
57
What did Wadatti contribute to sea floor spreading?
Investigated deep ocean trench off coast of Japan. Mapped earthquakes below surface (so directly under epicenter) noted it was an angled into the continent. Shallow at the trench and deeper at the land mass
58
What did Mason contribute to sea floor spreading -
Tested the strength of magnetic field at MORs found there was a pattern of strong signals at the ridge, and these pattern was mirrored on both sides of the ridge.
59
Explain paleo-magnetic reversal . How did it support sea floor spreading.
When magnetite crystals form in basalt, they will orient themselves to wherever magnetic north is at the time of formation. So you can track that the North Pole has flipped before.
If you mapped the orientation in these rocks on their side of the MOR, you’d find they were mirrored on each side of the ridge, indicating that the layers were torn in the middle and are moving apart
60
How could you test/support sea floor spreading?
Date the materials closer to the ridge and then farther away. The material closer to the ridge would be younger. You can even do this indirectly by just measuring the sediment accumulations rather than the actual basalt on the ocean floor.
Also found that there was way less sediment, or even no sediment at the ridge, less of a build up of layers and then it gets thicker with sediment the farther you get from MOR. So that’s another way to see that floor is spreading
Igneous rock layer at North American coast and Africa are the same age — indicates it was connected at some point.
The ocean floor is relatively young — found only rocks way younger than continent. If there wasn’t spreading the ocean floor would be the same age. (The ocean spreads then subducts under the continents, so it’s constantly getting created at MOR, then destroyed at continent).
Moving hot spots - if you look at Hawaiian islands, you see that the island with the current active volcanism is the youngest and it gets older which each farther island. The hot spots shows that the ocean floor is moving so the hot spots moves and creates islands.
61
Why is the Alvin submersive significant?
Sent to the MORs, saw pillow basalts from when the magma bleeds into the water and also black smokers — tells you active volcanism.
Also, found ecosystems down near the smokers and bacteria that live off of the sulfur created from the smokers. Using chemosynthesis rather than photosynthesis (ecosystem didn’t need sunlight). We used to think that life started in shallow pools, but maybe life started at the bottom of the ocean — would explain why we need metals in our bodies to live (Fe, Zn, Phosphorous) which is more commonly found in deep ocean places.
62
Describe the features of ocean-ocean convergent boundaries.
Two oceanic plates push up against each other, eventually one goes under or “sub-ducts” under the other. This is compressive stress “pushing”. Melting happens at the point where on plate is moving under the other. The magma is lighter so it will rise and become a volcano or island, like a volcanic island arc (which is diff from a hot spot created island). Earthquakes common and deep ocean trenches. Example would be the N American plate and Caribbean plate — N Amer plate is sub-ducting under, and that’s where there’s a lot of volcanoes and earthquakes in Caribbean, as well as the Puerto Rico trench.
63
How is an island created from a hot spots different from an island created from plate activity and associate volcanics (volcanic island arc).
For an island created from a hot spots, there’s usually just one of the islands that have an active volcano where on volcanic island arc there are many.
64
Describe continent-ocean plate convergence
The oceanic crust subducts under the much less dense and thicker continental crust. The lithosphere on continent will get thicker and you will see metamorphism. Melting magma created at point of convergence will rise, mix mafic magma with granitic continent making andesitic mix. Earthquakes common. Mountains are created from uplift as the ocean gets pushed under. You’ll see deep ocean trenches, volcanoes. An ex is Juan de Fuca plate being pushed under N Amer plate creating active volcanoes on northern part of the west coast.
65
Describe continent-continent boundary
There is no subduction, just thickening of lithosphere and crust. You see high mountains, folding and uplift. No volcanoes. Tons of earthquakes. EX: Indian plate into Eurasian plate
66
Describe what you see at a divergent boundary
The plates are pulling apart creating tensile stress. As you pull plate apart, the section that is getting pulled gets thinner and thinner and will eventually break. You will get a basin, with erosion on the walls and sediments accumulating. Magma can rise up at the tear point — is usually more mafic in composition. Ex: East Africa rift zone. Lots of volcanos. When you beginnings of rifting can break into three directions. If continue to pull apart can make a new ocean with MORs. The MORs are divergent boundaries and we see earthquakes and mafic volcanics.
67
Describe transform boundaries
Shear stress. Will also squeeze a little. you see small mountains. As the plates slide past each other, you create earthquakes. No volcanics. Ex: San Andreas Fault ZONE (not really a fault, more like a zone). Breakage occurs at boundary.
68
Do you only get earthquakes at plate boundaries? If yes, why? If no, why not?
You can have stress and faults in non-plate boundary areas. They USED to be boundaries from before Pangea broke apart. AN example would be the Palisades. Taconic Orogeny. There’s a fault at 125th street but they’re not big like in CA (being on a boundary)
69
Compared to today, during the last ice age sea level was: A) higher B) lower C) about the same
D) the seas disappeared E) none of the above
B. Lower
70
The type of seismic wave that doesn’t travel through both solids and liquids is: A) S waves
B) T waves C) P waves D) Z waves E) none of the above
A. S waves
71
If the flow rate of a glacier is greater than the melt rate (ablation rate), the glacial front (terminus)
will: A) advance B) retreat C) stand still D) completely disappear E) none of the above
A. Advance
72
The portion of the earth’s interior that is entirely liquid is: a) crust b) mantle c) outer core
d) inner core e) none of the above
C. Outer core
73
The semi-molten part of the upper mantle is called the _______
Asthenosphere
74
The semi-molten part of the upper mantle is called the _______
Asthenosphere
75
Describe 4 glacial features associated with glaciers. Include in your discussion how they formed
1. striations - dragging of drift, and large boulders carves into bedrock leaving grooves
2. Moraine - when flow rate equals ablation, the glacier keeps moving material forward like a conveyor belt, so it keeps dumping material. That material builds up at the terminus
3. Cirque - the “head” of a glaciated valley where the glacier originates creates this amphitheater or bowl like depression
4. Kettle lakes - when pieces of glacier break off when glacier retreats, will be stagnant and create a smaller depression on the ground which melt
76
Describe 4 pieces of evidence to back up a heterogeneous earth composition
1. Earthquakes and measuring S and P waves. If the earth was one material, then you would see the S & P waves on the other side of the globe, however, there are dead zones that support that something is either refracting the waves or killing them. Also, the waves move at different velocities, which means there are layers of different densities
2. Meteorites - show different compositions from what we just see on the crust.
3. Xenoliths - pieces of ultra mafic olivine come up with some lava flows. We know magma forms below earth crust so this must be piece of the mantle
4. The magnetic field - there needs to be a material that can do this.
77
A ridge of till formed when lateral moraines from two coalescing alpine glaciers form.
Medial Moraine
78
A ridge of till along the sides of a valley glacier composed primarily of debris that fell to the glacier from the valley walls.
Lateral moraine
79
A tributary valley that enters a glacial trough at a considerable height above the floor of the trough
Hanging valley
80
What is a recessional moraine?
An end moraine formed as the ice front stagnated during glacial retreat.
81
What is the general term for the loss of ice and snow from a glacier?
Ablation
82
What is the difference between an end moraine and a terminal moraine?
An end moraine is a ridge of till marking a former position of the front of a glacier whereas a terminal moraine denotes the farthest advance of a glacier.
83
What is a ground moraine?
The gently rolling layer of till laid down as the ice front recedes. They have a leveling effect filling in low spots and clogging old streak channels, often leading to a derangement of existing drainage system. Poorly drained swampy lands are quite common effect.
84
What are two examples of moraines in New York?
Ronkonkoma moraine and harbor hill moraine to the north of that both running length of LI
85
During the Pleistocene Epoch the amount of glacial ice in Northern Hemisphere was trice as great as in the Southern Hemisphere. Why is this the case?
Primary reason is that the southern polar ice could not spread far beyond the margins of Antarctica. By contrast, North America and Eurasia proved great expanses of land for the spread of ice sheets.
86
List three indirect effects of Ice Age glaciers.
The advancing and retreating glaciers forced species to migrate and some to die out
Many present day stream courses have changed, glacier modification to landscape carved them a new route.
Vertical crustal movement - as ice retreats, stops pushing the crust down, so now it’s rebounding without the heavy weight.
ALSO:
Fall and rise of sea level
87
How might plate tectonics help explain the cause of ice ages?
Glacial features in present day Africa, Australia and South America and India indicate that these regions which are now sub-tropical or tropical experiences an ice age at end of Paleozoic era (250 mya). Sciences, thru plate tectonics, realized that this area used to be joined together at latitudes far south of where they currently are.
88
45 Mya something cooled off the planet. One is one possibility for why this might have been?
India was a separate plate and began to crash into Eurasian plate. Created Himalayas and Tibetan plateaus. If you throw up continental crust, there are felsic materials like quartz, feldspar, and mica. When you weather feldspar, you use up CO2 (pulled from atmosphere). So that could have caused cooling.
89
What is the radius of the earth?
6378km
