fossil of a species that existed on Earth for only a short time
Index fossil
method to determine the order of events and relative age of rocks by examining the position of rocks in a sequence
Relative dating
gaps in the rock layers due to erosion
Unconformity
release of nuclear particles and energy from unstable atomic nuclei
Radioactive decay
states that Earth processes happening today are similar to those that happened in the past
Iniformitarianism
process to determine the absolute ages of rocks by measuring the amounts of parent and daughter materials in a rock
Radioactive dating
an active submarine ridge system situated in the middle of an ocean basin
Mid-ocean ridge
the relatively thin part of the earth's crust which underlies the ocean basins
Ocean crust
the relatively thick part of the earth's crust which forms the large land masses
Continental crust
the gases surrounding the earth or another planet
Atmosphere
the point on the earth's surface vertically above the focus of an earthquake
Epicentre
fine particles of rock dust blown from an explosion vent.
Ash
volcanic ash that has fallen through the air from an eruption cloud
Ashfall
a steep volcanic cone built by both lava flows and pyroclastic eruptions
Composite volcano
a volcano that consists of a complex of two or more vents, or an associated volcanic dome, either in its crater or on its flanks
Compound volcano
a passage followed by magma in a volcano.
Conduit
a volcano which is presently inactive but which may erupt again
Dormant volcano
the process that solid, liquid, and gaseous materials are ejected into the earth's atmosphere and onto the earth's surface by volcanic activity
Eruption
cracks on the slopes of a volcano
Fissures
springs that throw boiling water high in the air caused by volcanic heat warming trapped ground water
Geysers
magma which has reached the surface through a volcanic eruption with streams of liquid rock that flow from a crater or fissure
Lava
molten rock beneath the surface of the earth
Magma