8th Grade Science Test 2 Flashcards
the most abundant element in the earth’s crust
oxygen
in what type of fault do rocks along one side of the fault move horizontally along the fault
strike-slip fault
85% of all earthquakes are
shallow-focus earthquakes
a bowl-shaped hollow more than 2 miles wide, formed by the collapse of an underground magma chamber
caldera
the point deep in the earth at which an earthquake begins
focus
the large almond- or teardrop-shaped pieces of ejecta formed when lava solidifies
volcanic bomb
the narrow zone of active volcanoes that nearly encircles the Pacific basin
Ring of Fire
About 80% of the world’s earthquakes occur
in the circum-Pacific belt
the bending or buckling of rocks under great force produces
a fold
the inner core of the earth is thought to be
solid
an inactive volcano that can erupt again
dormant
the middle of the earth’s three main layers
mantle
an instrument used to record the vibrations caused by earthquakes
seismograph
a large, well-known strike-slip fault in western California
San Andreas Fault
the study of the earth
geology
the study of earthquakes
seismology
all the present-day continents are thought to have been one land mass called
Pangaea
an earthquake caused by sudden movements of rock beneath the earth’s surface
tectonic earthquake
a domelike igneous instrusion formed when magma bulges overlying rocks upward
laccolith
type of volcano consisting primarily of erupted volcanic ash and rock fragments held loosely together
cinder-cone volcano
broad, gently sloping volcano made of large quantities of highly fluid lava that hardened into rock
shield volcano
volcano formed partly by explosive eruptions of ash and rock fragments and partly by mild lava flows
composite volcano
theory that states that rocks spring back to a position of little or no strain at the moment of an earthquake, causing vibrations in the earth’s crust
elastic rebound theory
the fastest type of earthquake waves
P waves
small earthquakes that often follow a larger earthquake at frequent intervals for days or even months
aftershocks
the most famous scale of earthquake strength, which rates earthquakes on a scale of 1-9
Richter scale
deposits of sand and mineral fragments, usually laid down by water
sediments
the underground ___ is the actual source of a volcanic eruption
magma chamber
a sheetlike igneous intrusion formed when magma hardens in a vertical crack
dike
type of mountain formed when molten rock collects beneath an overlying rock layer, forcing the layer upward into a blisterlike structure
domed mountain
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
fault-block mountain
type of mountain formed when molten rock erupts from a hole in the earth’s crust
volcanic mountain
type of mountain formed when two rock layers are pushed together, causing the layers to buckle
folded mountain
the point on the earth’s surface directly above the point where an earthquake begins
epicenter
an archlike structure formed when rocks are folded upward
anticline
the channel in a volcano through which gases, ash, and molten rock are ejected from the earth’s interior
vent
a superheated, incandescent cloud of gas and volcanic ash that flows swiftly down a volcanic slope
pyroclastic flow
lava that hardens into rough, jagged rocks with a crumbly or “blocky” texture
aa lava
a troughlike structure formed when rocks are folded downward
syncline
lava that hardens into a smooth-textured rock with a “ropy” appearance
pahoehoe
a particle or block of solid volcanic ejecta
pyroclast
in what type of fault are rocks on one side of a fault shoved on top of the rocks on the other side
thrust fault
a volcano that has erupted within recorded history or is currently producing seismic activity
active
the central portion of the earth
core
Where are the effects of an earthquake most severe?
epicenter
In what kind of fault do rocks along one side of the fault sink vertically?
normal fault
What is the boundary line between the crust and the mantle called?
Mohorovicic discontinuity (Moho)
What is molten rock beneath the surface of the earth called?
magma
What theory states that the earth’s crust and upper mantle consist of huge plates slowly drifting because of convection currents in the mantle?
plate tectonics
What is the area between the upper mantle and the lower mantle called?
transition zone
What is an underground channel that formed when surface lava hardened before the lava underneath it?
lava tunnel
Compare and contrast fixed-base systems, base-isolated systems, and energy-dissipation devices.
A fixed-base system is a type of foundation in which the building is attached to bedrock; the energy of an earthquake is absorbed by the building’s frame and joints. A downside to this system is that the building may be deformed.
Base-isolated systems are the most common new construction for earthquake resistance. In a base-isolated system, the building is on stiltlike isolators, which separate the building from the foundation and absorb seismic energy.
Energy-dissipation devices are added to structures to absorb seismic energy, lessening the stress on the building and thereby minimizing deformation.
