Quiz 7-Ch 3/5 Flashcards
Regional Fault systems
often times the zone of deformation between two moving plates is not just one fault but rather a network of interacting faults called a fault system
Convergent boundaries
produces the world’s largest and deepest earthquakes along megathrusts under compressive stress
the deepest earthquakes occur in the oldest and therefore coldest descending plates
subduction (ocean-ocean)
one plate sinks beneath another into the asthenosphere and is recycled evenly through mantle convection which produces oceanic trenches
as the cold slab sinks the pressure on it increases and the water trapped in the slab is squeezed out and rises to the asthenosphere above. It melts mantle material and the resulting magma produces a chain of volcanoes called and island arc
ocean-continent
the continental plates overrides the oceanic plate because it is lighter and not as easily subducted. the submerged portion of the continent is crumpled causing earthquakes and tsunamies as well as mountain belts. as in ocean-ocean convergence the water from the rock creates a chain of volcanoes behind the deep sea trench
continent-continent
this collision creates a double thickness of crust where mountains are formed (i.e. Himalayas) severe earthquakes also occur
Transform fault boundaries
typically found along mid-ocean ridges. they can connect divergent-divergent boundaries and convergent-convergent boundaries
magmatic differentiation
a process by which rocks of varying composition can arise from a uniform parent magma.
This occurs because different minerals crystallize at different temperatures. The composition of magma changes progressively as various elements are withdrawn to crystallize minerals.
Fractional Crystallization
a process by which the crystals formed in a cooling magma are segregated from the remaining liquid
Bowen’s Reaction Series
crystals formed in a magma’s chamber settle to the bottom. then the magma moves to form new chambers thus leaving the crystals out of the rest of the reaction
Plutons
large igneous bodies formed deep in earth’s crust
They make room for themselves by wedging into, breaking off and melting surrounding country rock
Batholiths
largest plutons that are great irregular masses of course-grained igneous rock that cover at least 100km^2
sill
sheetlike body of magma that runs parallel to the surrounding country rock
They differ from lava flows in 4 ways: lack the ropy and vesicle filled structure, more coarse-grained, rocks above and below show effects of heating (change in color, composition etc.), sills do not overlie weathered lava flows or have soil formed in between successive flows.
dikes
small intrusive bodies that cut across rock
they rarely exist alone
Veins
deposits of minerals found in rock fractures that are foreign to the country rock
pegmatites
veins of extremely course grained granite cutting across a finer grained country rock crystallized from a water rich magma
