CH. 25 Sec. 3-4 Flashcards

1
Q

What is the boundary that marks a density change between layers?

A

Discontinuity.

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2
Q

How are discontinuities identified?

A

By studying seismic waves.

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3
Q

What are shadow zones?

A

An area where no seismic waves are recorded.

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4
Q

What is another term/name for shadow zones?

A

Dead zones.

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5
Q

Between what degrees do shadow zones fall?

A

105 to 140 degrees.

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6
Q

Is the outer core a solid or a liquid?

A

It’s a liquid.

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7
Q

Is the inner core a solid or a liquid?

A

It’s a solid because of so much pressure.

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8
Q

What makes up the lithosphere?

A

The crust and uppermost mantle.

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9
Q

What is the asthenosphere?

A

A plastic-like layer which Earth’s plates move.

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10
Q

What elements make up the mantle?

A

Calcium, aluminum, iron, and magneseum.

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11
Q

What elements make up the the core?

A

Iron and nickle.

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12
Q

The measure of a fluid’s resistance to flow.

A

Viscosity

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13
Q

The chemical compound silicon dioxide, SiO^2, which is a common ingredient in most magma.

A

Silica

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14
Q

They are small and have heights in the hundreds of meters of range, and have short eruption cycles.

A

Cinder cone volcanoes

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15
Q

They are broad, flat structures composed of layer upon layer of lava flows.

A

Shield volcanoes

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16
Q

Large and steep-sided, often thousands of meters high and tens of kilometers across the base, and composed of layers of both lava and ash.

A

Composite volcanoes

17
Q

What is molten or liquid rock stored inside the Earth called?

18
Q

Where is the Ring of Fire located?

A

Along the Pacific Ocean

19
Q

Melting can occur where?

A

In the asthenosphere

20
Q

Because the magma is less dense than the surrounding solid rock, it is forced to move which way?

A

Upward/rise to the surface

21
Q

Rising magma can reach Earth’s surface under what conditions?

A

If pressure conditions allow and conduits through which it can flow

22
Q

Eruptions are common where plates separate along mid-ocean ridges, continental rifts, and where plates collide along a subduction zones. They are also common where else?

23
Q

Volcanic eruptions occur in which areas?

A

Where plates separate along a mid-ocean ridge or where plates collide along a subduction zone

24
Q

Most of Earth’s volcanoes that are found along plate boundaries that surround the Pacific Ocean is called the ___________.

A

Ring of Fire

25
Volcanoes in the northwestern United States and Alaska form along subduction zones inside of what?
The Ring of Fire
26
There are places where volcanic activity occurs on land due to divergence, such as what attraction?
The East African Rift Valley
27
Why do most divergent plate boundary volcanic activity happen and yet are undetected?
Because they occur underwater along mid-ocean ridges.
28
Hot spots are areas of volcanic activity where magma moves toward the surface in large what?
Balloon-like plumes
29
What are two specific locations where volcanic activity occurs due to divergence?
The East African Rift Valley and the Mid-Atlantic Ridge
30
Are hot spots stationary?
Yes
31
What is viscosity?
The resistance to flow
32
If magma has a high viscosity, will it contain more or less silica?
It will contain more
33
What is pyroclastic material?
Any solid material that erupts from a volcano
34
What is the smallest type of pyroclastic material?
Volcanic ash
35
What is the largest pyroclastic material?
Blocks and bombs
36
What are the types of gases that erupt from a volcano?
Water vapour, carbon dioxide, and sulfur dioxide
37
How are volcanoes classified?
By size, shape, and the materials that erupt from it