The Solid Earth - Chapter 7: Igneous Activity and Plate Tectonics Flashcards
T/F: The earth’s crust and mantle are composed primarily of solid rock
True
Although the outer core is in a fluid state, this material is very ___ and remains deep within the earth
dense
True or false: the molten outer core is a source of magma
False
What is the most obvious way to generate magma from solid rock (geologists best guess of the origin)?
raise the temperature
Which melts first: basaltic rocks or silica rich rocks?
Silica rich
One source of heat to melt rock is the heat liberated during the decay of _______ found in mantle and crust
radioactive elements
At deep ocean trenches, slabs of cool oceanic lithosphere ____ into the hot mantle
descend
Where does the heat come from that melts the subducting oceanic crust and produce basaltic magma?
From the surrounding rocks
What, besides heat, increases with depth?
Pressure
Rock ___ when heated
expands
As a rock is heated, the first liquid to form will contain a ___ percentage of the low melting temperature minerals than the original rock
higher
Why do rocks sometimes melt across a span of several hundred degrees?
They are made of different materials with different melting points
A process that produces magma when melting is not complete
partial melting
True or false: most of the 600+ active volcanoes that have been identified are located near convergent plate margins
True
The greatest volume of volcanic rock is produced along the ____ ____ ___
oceanic ridge system
What is active in the oceanic ridge system that relates to a type of volcanism?
sea floor spreading
With spreading center volcanism, as the rigid lithosphere pulls apart, the pressure on the underlying rocks is _____
lessened
When the pressure on rocks is released, the melting temperature is ____
lowered
Which type of volcanism is associated with island arcs?
Subduction zone
In subduction zone volcanism, why would the melt slowly migrate upwards towards the earth’s surface?
It is less dense
As oceanic plates sink, they carry sediments and ocean crust containing ______ downward
water
Water ____ the melting point of rock
reduces
The source of some intraplate basaltic magma comes from rising plumes of hot ___ material
mantle
Hot plumes of mantle material in intraplate volcanism can potentially form what are known as…
hot spots
