CH. 25 Sec. 3-4 Flashcards
What is the boundary that marks a density change between layers?
Discontinuity.
How are discontinuities identified?
By studying seismic waves.
What are shadow zones?
An area where no seismic waves are recorded.
What is another term/name for shadow zones?
Dead zones.
Between what degrees do shadow zones fall?
105 to 140 degrees.
Is the outer core a solid or a liquid?
It’s a liquid.
Is the inner core a solid or a liquid?
It’s a solid because of so much pressure.
What makes up the lithosphere?
The crust and uppermost mantle.
What is the asthenosphere?
A plastic-like layer which Earth’s plates move.
What elements make up the mantle?
Calcium, aluminum, iron, and magneseum.
What elements make up the the core?
Iron and nickle.
The measure of a fluid’s resistance to flow.
Viscosity
The chemical compound silicon dioxide, SiO^2, which is a common ingredient in most magma.
Silica
They are small and have heights in the hundreds of meters of range, and have short eruption cycles.
Cinder cone volcanoes
They are broad, flat structures composed of layer upon layer of lava flows.
Shield volcanoes
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.
Composite volcanoes
What is molten or liquid rock stored inside the Earth called?
Magma
Where is the Ring of Fire located?
Along the Pacific Ocean
Melting can occur where?
In the asthenosphere
Because the magma is less dense than the surrounding solid rock, it is forced to move which way?
Upward/rise to the surface
Rising magma can reach Earth’s surface under what conditions?
If pressure conditions allow and conduits through which it can flow
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?
Hot spots
Volcanic eruptions occur in which areas?
Where plates separate along a mid-ocean ridge or where plates collide along a subduction zone
Most of Earth’s volcanoes that are found along plate boundaries that surround the Pacific Ocean is called the ___________.
Ring of Fire
Volcanoes in the northwestern United States and Alaska form along subduction zones inside of what?
The Ring of Fire
There are places where volcanic activity occurs on land due to divergence, such as what attraction?
The East African Rift Valley
Why do most divergent plate boundary volcanic activity happen and yet are undetected?
Because they occur underwater along mid-ocean ridges.
Hot spots are areas of volcanic activity where magma moves toward the surface in large what?
Balloon-like plumes
What are two specific locations where volcanic activity occurs due to divergence?
The East African Rift Valley and the Mid-Atlantic Ridge
Are hot spots stationary?
Yes
What is viscosity?
The resistance to flow
If magma has a high viscosity, will it contain more or less silica?
It will contain more
What is pyroclastic material?
Any solid material that erupts from a volcano
What is the smallest type of pyroclastic material?
Volcanic ash
What is the largest pyroclastic material?
Blocks and bombs
What are the types of gases that erupt from a volcano?
Water vapour, carbon dioxide, and sulfur dioxide
How are volcanoes classified?
By size, shape, and the materials that erupt from it
