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Earth Science > Interior of the Earth > Flashcards

Interior of the Earth Flashcards

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1
Q

How do we know about the structure of Earth’s interior?

A

We study how earthquake waves pass through Earth (seismology)

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2
Q

Order of Earth’s interior layers

A

Crust, mantle, outer core, and inner core

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3
Q

Coldest interior layer of Earth

A

Crust

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4
Q

Hottest interior layer of Earth

A

Inner core

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5
Q

Thickest interior layer of Earth

A

Mantle

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6
Q

Thinnest interior layer of Earth

A

Crust

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7
Q

Densest interior layer of Earth

A

Inner core

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8
Q

Which interior layers of the Earth are solid?

A

The crust, the inner core, and the mantle (behaves as a plastic)

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9
Q

Which interior layers of the Earth are liquid?

A

Outer core

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10
Q

What layer is under the most pressure? Why?

A

The inner core, because there is so much rock pushing on it from above

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11
Q

What is the core composed of?

A

The core is composed of a nickel-iron alloy

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12
Q

Why is the outer core liquid while the hotter inner core is frozen?

A
  • The inner core is under a lot of pressure, and pressure raises the melting point
  • In addition when a substance melts it expands, and due to the pressure the core can’t expand
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13
Q

When was the layered structure of Earth established?

A
  • 4.6 b years ago: planet so hot - entire thing liquid, no core yet- homogeneous: liquid rock and liquid iron throughout
  • As it cools off, pools of liquid iron (nickel, etc.), liquid rock and Liquid iron do not mix (immiscible), liquid iron is denser, goes to the center of the Earth (<50 million years old), shell of solid rock on surface
  • Inner core became solid about a billion years ago
  • Crystal of solid iron/nickel that grew
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14
Q

What causes the Earth’s magnetic field?

A

The flow of liquid iron in the outer core generates electric currents, which produce magnetic fields

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15
Q

Equation for the percentage of the volume of the core of a planet

A

Volume of a sphere: 4πr3 / 3

Percentage: Volume of core / Volume of planet

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16
Q

What are the most important sources of Earth’s internal heat?

A
  1. Radioactivity
  2. Leftover heat from Earth’s formation
  3. Pressure
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17
Q

Is the Earth cooling off or warming up?

A

The Earth is slowly cooling off

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18
Q

What is the difference between the asthenosphere and the lithosphere in terms of temperature, pressure, and rigidity?

A
  • The lithosphere consists of the crust and uppermost mantle and is rigid
  • It is colder than the asthenosphere and is less dense
  • The asthenosphere consists of the rest of the mantle and behaves as a plastic
  • It is warmer than the lithosphere and denser
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19
Q

What is a plate?

A
  • The outermost shell of the Earth, and consists of the crust and the rigid uppermost part of the mantle
  • They are transported across the surface of the Earth as they ride on the top of large mantle convection cells
  • 12 large plates + 12 smaller plates
20
Q

What are the differences between oceanic and continental plates?

A
  • Oceanic plates are denser and thinner than continental plates
  • They also tend to be younger, because they subduct at convergent boundaries
21
Q

What were the main pieces of evidence Wegener used to construct his theory on continental drift?

A

1) The continents seemed to fit together like a jigsaw puzzle
2) Fossils of prehistoric species were found on separate continents that would fit together if his theory was correct
3) Matching rock types were found on separate continents that would also fit together
4) Ancient glacial sediments found in places too warm for glaciers to form

22
Q

Why was Wegener’s theory not accepted for several decades?

A
  • He thought that the continents plowed through the rock of the ocean floor - disproved by geologic evidence
  • Continental drift was not accepted until Harry Hess had a hypothesis of seafloor spreading
23
Q

Divergent boundary

A
  • Ex: mid-Atlantic ridge
  • Where two plates are pulled apart from each other
  • Shallow earthquakes can occur (100 km)
  • Volcanic activity occurs due to decompression melting
  • Oceanic ridges are created, with a rift valley in the center
24
Q

Convergent boundary

A
  • Where two plates move toward each other
  • Shallow, intermediate, and deep earthquakes can occur
  • Volcanic activity occurs - melting of the mantle
  • Structures: trench, subduction zone, arc
25
Q

Transform boundary (ex)

A
  • Where two plates slide past each other
  • There can be shallow earthquakes (0-100 km)
  • No volcanic activity
  • Most occur in the middle of the oceans and connect segments of oceanic ridges (divergent margins)
  • Ex: San Andreas fault (California)
26
Q

Ocean-ocean convergent plate boundary

A
  • Where two oceanic plates meet and one is subducted beneath the other
  • The older plate (which is colder and denser) subducts beneath the younger one - denser
  • Ex: Philippines, Aleutian Islands, Lesser Antilles
27
Q

Ocean-continent convergent plate boundary (ex)

A
  • Where an oceanic plate meets a continental plate and the denser oceanic plate sinks beneath the less dense continental plate
  • Ex: Andes Mountains, Cascade Mountains
28
Q

Continent-continent convergent plate boundary (ex)

A
  • Where two continental plates collide with each other
  • Neither plate can sink beneath the other (can’t be subjected) because they both have low densities
  • Instead, the crust folds and enormous mountain chains are produced
  • Ex: Himalayas, Alps, Appalachians
29
Q

Where are the majority of earthquakes and volcanoes located?

A

At plate boundaries

30
Q

In what hemisphere are the majority of earthquakes and volcanoes located? Why?

A
  • In the northern hemisphere, there are more plate boundaries, which is where volcanoes form
  • They especially form at convergent boundaries, which the northern hemisphere has a lot of
31
Q

Alfred Wegener

A

A german meteorologist and climatologist who made the first hypothesis of the continental drift theory

32
Q

Arc

A

A line of volcanoes that forms parallel to the trench in a convergent boundary

33
Q

Asthenosphere

A

Consists of most of the mantle and behaves as a plastic

34
Q

Lithosphere

A
  • Consists of the crust and uppermost mantle and is rigid

- It is relatively cool and not dense

35
Q

Oceanic Ridge

A
  • Created at divergent margins
  • Long chains of mountains within ocean basins
  • In a few locations, so much volcanic activity has taken place that it forms volcanic islands (Iceland)
  • Rift Valley usually exists at center of ridge - represents the boundary between the two diverging plates
36
Q

Pangea

A

The supercontinent that formed 300 million years ago that broke apart 250 million years ago

37
Q

Panthalassa

A

The single large ocean that covered Earth’s surface during the time of the supercontinent Pangea

38
Q

Radioactivity

A

The emission of ionizing radiation or particles caused by the spontaneous disintegration of atomic nuclei

39
Q

Rigid

A
  • If an object is bent, it will go back to its original form if released
  • If it is bent too far, it will snap
40
Q

Subduction

A

When an oceanic plate begins to sink into the mantle

41
Q

Trench

A
  • A long depression where the oceanic plate begins to sink into the mantle
  • Pacific Ocean lined with trenches (Mariana Trench)
42
Q

Volcanic activity at divergent margins

A
  • Mantle melts due to decompression melting
  • Resulting mags ascends, erupts, and solidifies to create basalt (volcanic rock)
  • Basalt represents new oceanic crust
  • New crust forms - older crust pushed farther from ridge on either side
  • Result: youngest crust in the ocean basins is at mid-ocean ridges, oldest crust farthest from ridges - disappears into subduction zones close to continent
43
Q

Convergent margin earthquakes

A
  • Shallow, intermediate, and deep earthquakes can occur
  • Occur within upper part of lithosphere as it descends into the mantle
  • Below a depth of 700 km, the sinking lithosphere moves as a plastic and there are no earthquakes
44
Q

Convergent margin volcanic activity (ex)

A
  • Volcanic activity occurs because as the oceanic lithosphere sinks into the mantle, it heats up, forcing water to leave it and enter the mantle above the plate
  • This water lowers the melting point of the mantle
  • Product of this melting of the mantle: a line of volcanoes (an “arc”) over the subducted lithosphere
  • Examples: Mt. St. Helens, Mt. Pinatubo, Mt. Jujiyama, Krakatoa
  • Volcanoes often more explosive + dangerous - contain more gases such as water vapor and carbon dioxide
45
Q

Plate tectonics

A
  • The interaction of plates
  • Vast majority of earthquakes and volcanoes occur at the boundary between these plates
  • Explains why seafloor spreading and continental drift occur
46
Q

Magnetic evidence of seafloor spreading

A

-As lava cools, the iron-bearing minerals (mainly magnetite) align with the prevailing magnetic fields
-Evidence for geometric reversals first came from lava flows of various ages
-If you know how old the rocks are, you can determine when thee reversals were
Magnetometer. - device that measures strength of magnetic fields (over rocks with normal polarity = high magnetic strength, reverse polarity = low – cancel out)
Symmetrical pattern on either side of the ridge
-If you know when the reversal a specific point happened and how far away it is from the ridge, you can figure out how rapidly
-Key piece of evidence

Earth Science (16 decks)

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