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Geology 109 > Rocks > Flashcards

Rocks Flashcards

1
Q

What are the three main types of rocks?

A

Igneous, Metamorphic, and Sedimentary.

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2
Q

What are rocks made up of?

A

Groups of minerals.

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3
Q

How are Igneous Rocks formed?

A

By the cooling of molten magma.

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4
Q

How are Intrusive Igneous Rocks formed?

A

When magma cools slowly under the earths surface, it allows for large crystals to form.

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5
Q

What is an example of an Intrusive Igneous Rock?

A

Granite.

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6
Q

How are Extrusive Igneous Rocks formed?

A

When magma comes to the earths surface at a volcano, it is called lava. Lava cools faster (because of little insulation), and minerals that form are very small, or glasses are produced.

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7
Q

What are Metamorphic Rocks?

A

Metamorphic rocks form at depths under the earth when preexisting rocks are places under high degrees of heat and stress.

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8
Q

Where do Metamorphic Rocks usually form?

A

Usually in areas where mountain building is happening.

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9
Q

What are Sedimentary Rocks?

A

Rocks made up of pieces of older rocks that are produced on the Earth’s surface.

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10
Q

How are Sedimentary Rocks formed?

A

When rocks are exposed on the surface, they are weathered and eroded. These pieces of rock fragments are then deposited where they pile up and eventually turn into sedimentary rocks.

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11
Q

What are the two main ways that Earth’s crust rocks can react in response to the stresses and strains they are put under?

A

1) As a brittle structure and break

2) As a ductile material

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12
Q

When do crust rocks act as a brittle structure and break?

A

Occurs under low temperature and pressure on or near the surface.

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13
Q

When do crust rocks act like a ductile material?

A

Occurs under high temperature and pressures when rocks are buried at depth.

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14
Q

What two types of structures are made in regards to stresses and strains on Earth’s crust?

A

Folds and faults, ranging from centimetres to 10s of kilometres large.

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15
Q

What does Strike and Dip describe?

A

Folds and faults.

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16
Q

What is the Strike?

A

The direction of the intersection of a rock layer with a horizontal surface.

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17
Q

What is the Dip?

A

The amount of tilting of the rock measured at 90 degrees from the strike.

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18
Q

What three types of forces can deform rocks?

A

1) Compressive forces
2) Tensional forces
3) Shearing forces

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19
Q

What is a Compressive Force?

A

A squeezing force (compresses inwards).

20
Q

What is a Tensional Force?

A

A pulling force (pulls away).

21
Q

What is a Shearing Force?

A

A twisting/bending force.

22
Q

What is an Anticline fold?

A

Happens when rocks are hot, under pressure, ductile and under compressive forces. Creates an arch.

23
Q

What is a Syncline fold?

A

Happens when rocks are hot, under pressure, ductile, and under compressive forces. Creates a dip.

24
Q

What do folds often alternate as?

A

Syncline and Anticline folds along the limb and axial.

25
Q

What are Faults classified based on?

A

The type of motion along the break in the rock, which is controlled by the type of stress the rock is under.

26
Q

What is a Normal Dip-Slip Fault?

A

The Foot Wall moves up relative to the Hanging Wall.

27
Q

What force causes a Normal Dip-Slip Fault?

A

Tensional forces.

28
Q

What is a Reverse Dip-Slip Fault?

A

The Hanging Wall moves up relative to the Foot Wall.

29
Q

What force causes a Reverse Dip-Slip Fault?

A

Compressive Forces.

30
Q

What is a Strike Slip fault?

A

When the rock moves past each other on the strike (horizontal to each other) and occurs under shearing forces.

31
Q

What did geologists believe about the Earth’s crust until early in the 20th century?

A

That the Earth’s crust was static (unmoving), but that began to change as geologic knowledge improved.

32
Q

What is the modern thought about the Earth’s crust?

A

This is it broken into pieces called plates that are constantly moving.

33
Q

What is the Continental Drift theory?

A

The first theory about the motion of continents, popularized by Alfred Wegener. The continents moved through the oceanic crust, which stayed fixed. Initially suggested that the continents moved by tidal influences of the moon.

34
Q

What different Plates are there?

A

Eurasian, Australian, Pacific, North American, South American, African, and Nazca Plate.

35
Q

What evidence existed for the Continental Drift?

A

The main line of evidence used is how the continents fit together, and many geologic formations continue across continents.
There is evidence for glaciation in many southern locations in the Late Paleozoic - if the continents were in current location, the centre of glaciation would have been in the ocean.
Similar fossils found in different continents.

36
Q

What was the Theory of Plate Tectonics built on?

A

Introduced in 1968, it was build primarily on evidence gathered in the 50s and 60s from the oceans floors and was a much more encompassing theory that Continental Drift.

37
Q

What is Paleomagnetism?

A

When molten rocks cool down, the iron in them points toward the north pole, which allows geologists to figure out where the magnetic North Pole was in the past.

38
Q

What temperature does molten rock cool down at?

A

The Currie Point.

39
Q

How did Paleomagnetism support the Theory of Plate Tectonics?

A

Scientists began mapping the location of the North Pole, and found that it did not match up unless the continents moved. Surveys of the ocean floor also found alternating magnetic normal and reversed rocks spreading out from Mid-Ocean Ridges (best explained by sea floor spreading).

40
Q

What are Hot Spots?

A

Chains of volcanoes that are formed as plates move over stationary hot spots. This supported the Theory of Plate Tectonics.

41
Q

Where do Earthquakes primarily occur?

A

On late margins.

42
Q

Where do Earthquakes get deeper?

A

At convergent margins as the plate is subducted.

43
Q

What is the current belief behind how the Plates moved?

A

It is believed that convection currents (like in a pot) in the mantle push the plates of crust along.

44
Q

What happens at Divergent Margins?

A

New oceanic crust is produced, the margin causes plates to spread apart, and oceans to widen.

45
Q

What happens at Convergent Margins?

A

This is where two plate collide, and what happens depends on the type of plates colliding. The older crust will be more dense than the younger crust, and be pushed underneath.

46
Q

What kinds of Convergent Margin collisions can there be?

A

Ocean-Ocean, Ocean-Continent, or Continent-Continent.

47
Q

Which is more dense: Oceanic Crust or Continental Crust?

A

Oceanic Crust - it will always be condensed below Continental Crust.

Geology 109 (17 decks)

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