Chapter 25. 3 Flashcards
What is the boundary that marks a density change between layers ?e
Discontinuity
How are discontinuities identified ?
By studying seismic waves
What are shadow zones ?
Shadow zones are areas where no seismic waves occur.
What is another term for shadow zones ?
Dead zones
What are the degree ranges which shadow zones are formed ?
Between 105 and 140 degrees from the epicenter
Is the outer core a solid or a liquid ?
Liquid
Is the inner core a solid or liquid ? Why?
Solid and it is a solid because of the amount of pressure
What makes up the lithosphere ?
Crust and uppermost mantle
What is the asthenosphere ?
A plastic like layer which Earth’s plates move
Which elements make up mantle ?
Calcium, Aluminum, Iron, and Magnesium
What elements make up the core ?
Iron and Nickel
Viscosity
The measure of a fluid’s resistance to flow
Silica
the chemical compound silicon, SIO subscript two, is a common ingredient in most magma
Cinder Cone Volcanoes
Tend to be small in range, have heights in the hundreds of meters range, and have short eruption cycles
Composite 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
Shield Volcanoes
broad, flat structures composed of layer upon layer of lave flows
Where can melting occur ?
In the asthenosphere
Why does magma rise ?
it is less dense than the surrounding rock
How does magma rise ?
Magma rises is the pressure conditions allow and there are conduits in the rock
Where do volcanic eruptions occur ?
Volcanic eruptions occur where plates separate along a mid oceanic ridge or collide along a subduction zone
Where are most of Earth’s volcanoes located ?
They are located along plate boundaries that surround the Pacific Ocean called the Ring of Fire
How do volcanoes form ?
Volcanoes form where tectonic plates collide along subduction zones ?
Example :
Volcanoes the northwestern United States and Alaska form along subduction zones within the Ring of Fire.
What are hot spots ?
Hot Spots are areas of volcanic activity that where magma moves toward the surface in large, balloon like plumes.
Where do Hot Spots originate ?
Scientists believe that these plumes originate near the core-mantle boundary and that they are stationary
