lecture 25
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What is melting?
When the subducting plate, due to water, has a lower melting point causing the rock to melt as it gets closer to the mantle. The magma then ascends and reachs the surface to form an island arc
What is an example of a volcanic island arc?
The aleutian islands
What is the rink of fire?
A direct consequence of plate subduction
What is an example of an oceanic-continental convergent plate boundary?
The cascades and the Andes
Why does oceanic crust ALWAYS subduct under continental?
Because oceanic crust is denser than continental, which is light and floats on top of the mantle
What runs parallel to the subduction zone in an oceanic-continental convergent boundary?
the volcanic chain that makes up many volcanic ranges such as the Cascades
What happens when two continental plates converge?
Continental crust is light and buoyant, so when two continental crusts converge, a large mountain range is formed (Himalayas)
What happens at a transform boundary?
A plate boundary where two plates slide past one another
What is an example of a transform boundary?
The San Andreas fault
What do mantle plumes form?
Hot spots
What are mantle plumes?
They are a localized zone of hot magma in the mantle that is buoyant and rises from the core/mantle boundary, but is not at a plate boundary.
What is the key characteristic of mantle plumes?
They are in a fixed space, creating a linear chain of volcanoes as the plate slowly passes over it.
What is an example of a mantle plume?
Hawaii, where volcanic islands of the NW are progressively over and smaller due to erosion, and shows the direction of the Pacific plate
The theory of plate tectonics provides us with a conceptual framework of?
understanding the distribution of different geological activites and types of rocks at the Earth’s surface
What are the 3 major types of rocks?
igneous, sedimentary, and metamorphic
How are igneous rocks formed?
The melting of rocks in hot, deep crust and upper mantle. Formed by the cooling and solidification of magma or lava
How are sedimentary rocks formed?
Weathering and erosion of rocks exposed at surface. Result of the consolidation (lithification) or accumulation of sediments. Can be precipitated out of solutions from dissolved ions
How are metamorphic rocks formed?
Rocks under high temperatures and pressures in deep crust and upper mantle. Formed from a pre-existing rock by subjecting it to high temp and pressure but without melting, changing chemical composition and physical texture/look
What is the difference between a mineral and rock?
Rocks are composed of minerals (granite is quartz, homblende, and feldspar), and minerals exist in everything around us
What are the two types of igneous rocks?
Extrusive and intrusive
What is an extrusive igneous rock?
Forms from lava above ground, cools faster, has smaller crystals (minerals), meaning it is fine-grained. An example is basalt (seafloor)
What is an intrusive igneous rock?
Forms from magma below ground, cools slower, has larger crystals (minerals), meaning it is coarse grained. An example is granite in continental crust
What is the difference between granite and rhyolite?
despite having the same chemical composition, granite is large minerals and slow cooling, and rhyolite has tiny minerals and is fast cooling
What plate boundary forms igneous rocks and give an example?
Divergent, the palisades made up of diabase