chapter 21 Flashcards
crust
the thin and solid outermost layer of Earth above the mantle
mantle
the layer of rock between earth’s crust and core. because S-waves travel through mantle, it has to be a solid
earth’s core
the center of earth below the mantle, believed to be made of mostly iron and nickel inner core solid metal & outer core liquid metal.
inner core
the pressure is so great that the atoms are forced together as a solid despite the intense heat.
outer core
the pressure is so great that the substances are prevented from changing into gaseous form, so they stay liquid.
lithosphere
the solid, outer layer of earth that consists of the crust and the rigid upper mantle.
divergent boundary
occurs where two plates move apart, creating a gap between them. magma rises between the plates to fill the gap, creating a rift valley.
magma
liquid rock produced under earth’s surface
subduction
the process by which one lithospheric plate moves beneath another, as a result of tectonic forces. Ocean trenches, mountains, and volcanos are formed at subduction zones.
fault
a crack in the earth created when rocks on either side of a break move.
focus
the area along a fact at which the rift motion of an earthquake occurs. i.e.. the exact source of the earthquake
epicenter
the point on earth’s surface directly above an earthquake’s focus.
earthquake waves
Prime wave (P-wave): longitudinal wave. Secondary wave (s-wave) traverse wave. + surface waves.
Surface waves
a seismic wave that only moves through solids. So the S wave do travel through the crust and the mantle, but not through the core, cuz the outer core is liquid.
vent
an opening at the surface of earth through which volcanic material passes.
a volcano
any opening in earth’s crust through which magma has reached earths surface.
lava
when magma reaches the surface it’s physical behavior changes and it is called lava.
3 types of volcanoes
(1) shield, (2) composite, (3) cinder.
shield volcanoes:
have mild eruptions. Magma rich in iron and magnesium is very fluid and forms lava that tends to flow great distances.
composite volcanoes
have trapped gas. Made up of alternating layers of ash, cinders, and lava. Their magma is rich in silica and therefore is much more viscous than the magma of a shield volcano.
cinder cones
are the smallest and the most abundant volcanoes. When large amounts of gas are trapped in magma, violent eruptions occur — vast quantities of ash and lava are thrown from the vent.
seamount
underwater volcano. occur at divergent plate boundaries.
most volcanoes occur at
convergent plate boundaries.
earthquakes occur as a result of sudden movement within earth’s …
lithosphere.
most volcanoes occur at …
convergent plate boundaries.
P-waves
are the longitudinal waves and they travel the fastest.
S-waves
are transverse waves and they move more slowly. They travel only through solids – they can’t travel through the core cuz the outer core is liquid
surface waves
travel the slowest, they result from the earth vibrating like a bell.
mineral
a natural, usually inorganic ,solid that has a characteristic chemical composition, an orderly internal structure, and a characteristic set of physical quantities.
igneous rock
rock that cools and solidifies when magma cools.
obsidian
a smooth stone extrusive ingenious rock that cools much more quickly than granite. Obsidian has either very smalls crystals or no crystals at all and is mostly glass. Extrusive rock because it cools on the earth’s surface.
Extrusive rock
it cools on the earth’s surface.
Granite
intrusive igneous rock. coarse grained because it cools very slowly while trapped beneath the earth’s surface. Hence large crystals, because of long cooling time.
sedimentary rock
a rock formed from compressed or cemented layers of sediment. Ex. limestone, a sedimentary rock, will turn into marble, sedimentary rock, under the effects of heat and pressure.
metamorphic rock
a rock that forms from the other rocks as a result of intense heat, pressure, or chemical process.
old rocks in the rock cycle create new rocks.
rocks can change type as described by the rock cycle.
water expands ?% when it freezes.
~10% –> it can act as a wedge in weathering rocks.
