Ch. 25.3 & 25.4 Flashcards
What is the boundary that marks the density change between layers?
Discontinuity
How are discontinuities identified?
Using Seismic Waves
What are shadow zones?
Areas where no seismic waves are recorded
What is another term for shadow zone?
Dead Zone
Between what degrees do shadow zones fall?
105 to 140 degrees
Is the outer core a solid or liquid?
Liquid
Why is the inner core a solid?
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 Magnesium
What elements make up the core?
Iron and Nickel
The measure of a fluid’s resistance to flow…
Viscosity
The chemical compound silicon dioxide,SiO2, which is a common ingredient in most magma…
Silica
Tend to be small, have heights in the hundreds of meter range, and have short eruption cycles…
Cinder Cone Volcanoes
Broad flat structures composed of layer upon layers 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 happens when magma reaches Earth’s surface and erupts as lava or ash?
A Volcano
Where are most volcanoes located?
Plate Boundaries surrounding the Pacific Ocean called the Ring of Fire
Volcanic activity happens along what plate boundary?
Divergent
What is two example of volcanic activity due to divergences?
East African Rift Valley and Mid Atlantic Ridge
What are hot spots?
Areas of volcanic activity where magma moves toward the surface in large, balloon like plumes
Do hotspots move?
No they are stationary
Magma with high viscosities contain more?
Silica
Magmas with high water content have low?
Viscosities
