Abeka 8th grade Science Test 2

geology

Study of the earth

crust

the earth's outer layer made of solid rock

sediments

deposits of sand, mineral fragments, or organic materials usually left by wind or water

oxygen

most abundant element in the earth's crust

Moho

boundary between crust and mantle

core-mantle boundary

lies roughly 2900 km beneath the surface and marks the bottom of the mantle (between mantle and core)

inner core

by contrast, is thought to be solid iron or nickel, kept in solid state by pressures over 3.5 million

fault

when a layer of rock breaks and moves due to the strain of the forces upon it

thrust fault

results when rocks on one side of a fault are shoved on top of the rocks on the other side

syncline

rocks that bend downward during the folding process from a tough-like structure called a ______

folded mountains

these are thought to have formed when the edges of two adjacent tectonic plates were pushed together, causing the layers to buckle like a wrinkled rug

tectonic earthquakes

earthquakes that result from sudden movements of rock beneath the earth's surface

aftershocks

smaller earthquakes or tremors that often follow an earthquake at frequent intervals for days or even months, gradually decreasing in intensity

seismology

The study of earthquakes

elastic rebound theory

rocks on either side of a fault spring back to a position of little or no strain at the moment of an earthquake, triggering vibrations in the earth's crust

slickensides

Rocks along a fault may be polished smooth by this motion producing smooth faced fault scarps

Circum-Pacific Belt

80% of all earthquakes occur here

p waves

fastest traveling seismic waves

seismogram

a record produced by a seismograph

Modified Mercalli Scale

a system for describing and evaluating the effect of an earthquake on a man. it has twelve degrees of intensity

moment magnitude scale

considered the most reliable method for measuring an earthquake's magnitude

fixed-base system

base isolated system

essay: know all the base systems

energy dissipating devices

these devices are added to structures to absorb some of the seismic energy. this lessens the stress on the building, minimizing deformation.

volcano

an opening in the earth's surface through which hot gases, ash, and molten rock are ejected from the earth's interior

vent

the central feature of a volcano is what?

magma chamber

this vent reaches from the surface to a reservoir of molten rock called ________ _______

magma chamber

the actual source of a volcanic eruption

cinder-cone volcanoes

volcanoes that consist primarily of erupted volcanic ash and rock fragments called cinders

composite volcano cone

forms partly through explosive eruptions of cinders from the crater and partly through mild lava flows that pour out of cracks on the cone's flanks

dormant volcano

an inactive volcano that could erupt again

extinct volcano

volcano that is unlikely to erupt again

pahoehoe

lava that hardens to form either a smooth surface or a surface that resembles ropes

aa

lava that hardens into rough, jagged rocks with a crumbly texture

pillow lava

lava solidifies almost instantly and forms rounded structures resembling pillows

pyroclast

particles or blocks of solid volcanic ejecta

volcanic ash

consists of pyroclastic particles less than 2 mm in diameter

lapilli

ejecta that are larger than volcanic ash particles but less than 64 millimeters in diameter

volcanic blocks

solid, irregularly shaped lumps of hardened lava, often large and boulder-like in their appearance

volcanic bombs

form when lava is thrown high into the air in a liquid semi-liquid state and hardens into rock before it hits the ground

pyroclastic flow

consists of a superheated cloud of gas and volcanic ash that travels swiftly down the volcanic slope as an avalanche

volcanic explosivity index

a scale to measure the explosiveness of a volcano's eruptions

calderas

huge bowl shaped craters thought to form when the magma chamber beneath a volcano is emptied of magma causing it to collapse under its own weight

lava tunnels

form when the surface of a large lava flow hardens but the lava beneath remains molten and continues to flow

dike

when volcanic magma hardens in a vertical, sheet-like mass of igneous rock called a ______

laccolith

if the intruding magma is unusually stiff it may not flow easily enough to spread between rock layers to form a sill. instead, it bulges the overlying rocks upward to produce a dome-like intrusion called a ___________

shallow focus

85% of earthquakes are this type

focus

the point deep in the earth at which an earthquake begins

Ring of Fire

a narrow zone of active volcanoes that nearly encircles the Pacific basin is the

fold

The bending or buckling of rocks under great force

mantle

the middle of the earth's three main layers

Seismograph

used to record the vibrations caused by earthquakes

San Andreas Fault

A large, well-known strike-slip fault in western California.

Pangaea

term for the super continent which contained all the plates together

shield volcano

broad, gently sloping volcano made of large quantities of highly fluid lava that hardened into rock

Richter scale

the most famous scale of earthquake strength

magma chamber

the underground __________ _____________ is the actual source of volcanic eruption

domed mountain

type of mountain formed when molten rock collects beneath an overlying rock layer, forcing the layer upward into a blisterlike structure

fault-block mountains

type of mountain formed when rocks on one side of a fault are forced upward and the rocks on the other side are forced downward

volcanic mountian

a type of mountain formed when molten rock erupts from a whole in the earth's crust

epicenter

point on Earth's surface directly above an earthquake's focus

anticline

A fold in rock that bends upward into an arch

vent

the channel in a volcano through which gases, ash, and molten rock are ejected from the earth's interior

active

a volcano that has erupted within recorded history or is currently producing seismic activity

core

The central part of the earth below the mantle

epicenter

where the earthquakes effects are most severe

normal fault

rocks along the side of the fault sink vertically

magma

Molten rock beneath the earth's surface

plate tectonics

theory that the earth's crust and upper mantle consist of huge plates slowly drifting because of convection currents in the mantle

transition zone

the area between the upper mantle and the lower mantle