Geology exam 2

What is the composition of the remaining melt after a basaltic magma has fractionally crystallized olivine and some pyroxene?

Intermediate- The more you melt something the more felsic it becomes.

What feature do divergent continental boundaries turn into after millions of years of divergence?

Mid-ocean ridge- Divergent boundaries start inside of continents

What composition magma do you form when you partially melt an andesite?

More felsic

What is the first mineral to crystalize from a mafic composition magma?

Olivine: Bowen's reaction series. Olivine crystalizes first on the chart

Where does the water come from to cause hydrous melting in subduction zones? a) Water is bound in the crystal lattice of minerals in the oceanic lithosphere b) Water is trapped in the pores of subjecting sediments c) Water percolates in through faults

a)

What causes melting at divergent plate boundaries? a) Decompression Melting b) Increasing temperature c) Hydrous melting (adding water) d) Increasing both temperature and pressure

a) decompression melting A divergent plate melting has an upwelling mantle. As the pressure decreases, it is more likely that the mantle will melt. As it gets closer to the mantle, it will melt.

What causes melting at continental hot spots? a) Decompression melting b) Increasing temperature c) Hydrous melting (adding water) d) Increasing both temperature and pressure

a) decompression melting Hot rock (mantle) is less dense, and rising, through the mantle, to the surface. As pressure decreases, the mantle melts. [worksheet on divergent boundaries]

_____ tend to occur at subduction zones, ____ tend to occur at oceanic hot spots

b) Stratovolcanos are created out of felsic & mafic material. In order to get felsic and mafic, you need a subduction factory, so the magma has time to go from basalt to differential volcanos.

What causes melting at convergent plate boundaries? a) Decompression melting b) Increasing temperature c) hydrous melting (adding water) d) Increasing both temperature and pressure

c) hydrous melting 1. The ocean lithosphere with hydrous minerals subduct. 2. These minerals break down under high temperature and pressure 3. Buoyant fluids rise into the asthenosphere 4. Melting point of peridotite decreases, mantle melts.

Earthquakes occurs in the ________ at oceanic divergent boundaries and have relatively ________ magnitude. a) asthenosphere, low b) asthenosphere, high c) lithosphere, low d) lithosphere, high

c) lithosphere, low No enormous earthquakes are happening at oceanic boundaries. They always occurs in the lithosphere.