Permanent ice that is found mostly around Greenland and Antarctica.
ice core
Cylinder of ice extracted from a glacier or ice sheet.
ice wedging
Water enters a crack, expands as it freezes, and wedges the rock apart.
igneous rock
A rock formed from cooled magma.
impermeable
Something that water cannot penetrate.
import
To receive a resource or product from another country.
independent variable
The variable in an experiment that is controlled and changed by the researcher.
index fossil
A fossil indicates the relative age of the rock in which it is found. Index fossils come from species that were widespread but existed for a relatively brief period of time.
Industrial Revolution
A time when mass production and fossil fuel use started to grow explosively.
infrared light
Electromagnetic waves with frequencies between radio waves and red light.
inner planets
The four planets inside the asteroid belt: Mercury, Venus, Earth, and Mars.
inorganic
Not organic; not involving life or living organisms. For example, the rock and mineral portion of the soil.
insolation
The amount of solar radiation striking a given area over a given period of time.
insulation
A material that inhibits conduction of heat or electricity.
intermediate
A type of igneous rock that is in between felsic and mafic.
intertidal zone
The part of the ocean closest to the shore, between low and high tide.
Intertropical Convergence Zone (ITCZ)
A low pressure zone where the Hadley Cells at the equator meet.
intraplate activity
Geologic activity that takes place away from plate boundaries.
intrusive
Igneous rocks that form inside the Earth from slowly cooling magma.
invasive species
A species of organism that spreads in an area where it is not native. People often introduce invasive species either purposefully or by accident.
inversion
A situation in which warm air lies above cold air.
invertebrate
Animal with no backbone.
ion
An atom with one or more electrons added or subtracted; it has an electrical charge.
ionic bond
A chemical bond in which atoms give or accept atoms.
ionosphere
An ionized layer within the thermosphere.
irregular galaxy
A galaxy that is neither spiral nor elliptical.
island arc
A line of ocean island volcanoes resulting from subduction beneath oceanic lithosphere.
isobars
Lines connecting locations that have equal air pressure.
isotachs
Lines connecting locations that have equal wind speed.
isotherms
Lines connecting locations that have equal temperatures.
isotope
A chemical element that has a different number of neutrons.