Download changing earth chap 1 vocab

crust
The thin outer layer
of Earth. Earth’s
crust varies from 5
km to 48 km in
thickness.
mantle
The middle layer of
Earth. The mantle is
the thick layer of
rock between the
crust and core.
core
The center of the earth.
Made up of two parts:
the inner core and the
outer core.
magnetic
field
The space around a magnet
within which the force of the
magnet is exerted. The
magnet attracted all the iron
fillings within its magnetic
field.
magnetic
reversal
The switching or changing of Earth’s
magnetic poles such that the north
magnetic pole becomes located at
the south magnetic pole’s position
and vice versa. Scientists have
found evidence of magnetic
reversals in layers of rock along the
ocean floor.
mid-ocean
ridge
A chain of mountains under
the ocean. The mid-ocean
ridge extends almost 60,000
km.
plate
boundaries
A place where the plates that make
up earth’s crust and upper mantle
either move together or apart or
else move past each other.
sea-floor
spreading
The process by which new ocean
floor is continually being formed as
magma rises to the surface and
hardens into rock. Sea-floor
spreading occurs as magma fills the
space between separating plates.
tectonic
plates
One of the slabs that make up
Earth’s crust and upper mantle.
Some of Earth’s tectonic plates
carry continents.
Theory of
Continental
Drift
A theory that states that the
continents formed a single land mass
at one time in the past and have
drifted over time to their present
positions. The idea of continental
drift was first suggested by Alfred
Wegner.
Theory of
Plate
Tectonics
The theory that the Earth’s
lithosphere is broken into enormous
slabs, or plates, that are in motion.
Scientists use the theory of plate
tectonics to explain how the
continents drift.
Pangaea
A super-continent that existed
over 200 million years ago.
Pangaea broke apart into
several continents.