The Geosphere
• luster
• mantle
• streak
• lithosphere
• cleavage
• asthenosphere
• fracture
• core
• crust
Materials in the Geosphere
• The basic building blocks for soil, rocks,
and metals are minerals.
• Minerals combine in different ways,
forming the other materials in the
geosphere.
Materials in the Geosphere
• A mineral is a naturally
occurring, inorganic solid
with a crystal structure
and definite chemical
composition.
• Properties such as color,
crystal shape, luster,
streak, hardness,
cleavage, and fracture can be used
to identify minerals.
Mark Schneider/Getty Images
Materials in the Geosphere (cont.)
• Luster is the way a mineral’s
surface reflects light.
• Streak is the color of a
mineral’s powder. It is
observed by scratching
a mineral across a tile of
unglazed porcelain.
DEA/A.RIZZI/Getty Images
• The hardness of a mineral can be
ranked on a scale of 1 to 10 on the Mohs
scale, with 1 being the hardest.
Materials in the Geosphere (cont.)
• Cleavage is the tendency of minerals to
break along smooth, flat surfaces.
• Fracture is the tendency of minerals to
break along irregular surfaces.
• Some minerals tend to break apart and
combine with other substances, while
other minerals are more stable and
durable.
Materials in the Geosphere (cont.)
• A rock is a naturally occurring solid
composed of minerals and other
materials.
• Rocks are classified according to how
they form.
• The three main types of rocks are
igneous, metamorphic, and sedimentary.
Earth systems interact in the rock cycle.
Materials in the Geosphere (cont.)
• Igneous rock forms when molten rock
material cools and hardens.
• Metamorphic rock forms when
sedimentary, igneous, or other
metamorphic rocks are subjected to high
temperatures and extreme pressure.
• Sedimentary rocks form when sediment
is eroded by water, wind, ice, or gravity
and deposited in layers.
Materials in the Geosphere (cont.)
• The formation
of sedimentary
rocks involves
interactions
among all Earth
systems.
• Rocks can be broken down by physical
and chemical weathering.
Soil is the loose, weathered
material in which plants grow.
• Soil layers form as rock is slowly
transformed into soil.
• Soil formation begins when rocks
weather into sediment and water
dissolves minerals and other materials
from the
sediment.
Materials in the Geosphere (cont.)
• Wastes from organisms and the
decaying bodies of dead organisms
provide soil with nutrients that makes
it more fertile.
• A major part of the organic matter in soil
is carbon that plants obtain from the
atmosphere through photosynthesis.
• Soil plays a major role in the phosphorus
and carbon cycles.
Interactions among all Earth systems take
place in soil because soil contains minerals,
water, air, and organisms, all in close
contact.
Structure of the Geosphere
• The geosphere
has three main
layers: the crust,
the mantle, and
the core.
• The densest layer
of the geosphere
is the center, or
core, and the least
dense layer is the
outer crust.
Structure of the Geosphere (cont.)
• Scientists hypothesize Earth’s layers
formed early in the planet’s history.
• Ancient Earth was much hotter than it is
today and thermal energy melted some
of the rock.
• Gravity pulled denser materials through
the melted rock toward Earth’s center,
forming layers.
Structure of the Geosphere (cont.)
• Each of Earth’s layers has a different
density.
• Most of the geosphere is made of solid
rock, but some of it is made of metal.
Structure of the Geosphere (cont.)
• Scientists know about the makeup of
Earth’s deep inner layers from gathering
data by analyzing earthquake waves.
• When the waves travel through Earth,
they change speed and direction when
they pass through materials with different
densities.
• The crust is the thin outer layer of the
geosphere.
• Oceanic crust is made of the dense
igneous rocks basalt and gabbro.
Continental crust, which is thicker but less
dense than oceanic crust, is made of
igneous, metamorphic, and sedimentary
rock.
• The mantle
is the thick,
rocky middle
layer of the
geosphere.
• The mantle has
the largest volume
of any layer of Earth,
and much of it is
made of the rock
peridotite.
• The crust
and the
uppermost
mantle form
a brittle outer
layer called the
lithosphere.
• The weak,
partially melted
layer of the
mantle is called the asthenosphere.
Structure of the Geosphere (cont.)
• The dense, metallic center of Earth is
called the core.
• The core is made mainly of iron with
some nickel and traces of other
elements.
• Due to the high temperatures near the
center of the Earth, the outer layer of the
core is liquid.
Scientists theorize that the movement of
liquid iron in the outer core produces
Earth’s magnetic field.
Structure of the Geosphere (cont.)
• Inside the outer core is a sphere of solid
metal.
• Despite the scorching heat, the metal in
the inner core is not melted.
• The high pressure from the masses of all
Earth’s layers compresses the inner
core, making it solid.
• Minerals are the basic building
blocks for materials in the
geosphere, including soil, rock, and
metal.
• The three main
layers of the
geosphere are
the crust, the
mantle, and the core.
• The layers of
the geosphere
have different
densities and
chemical
compositions.
What is the color of a mineral’s
powder, observed by scratching a
mineral across a tile of unglazed
porcelain?
A. cleavage
B. fracture
C. luster
D. streak
What is the loose, weathered
material in which plants grow?
A. mantle
B. soil
C. geosphere
D. rock fragments
What is the weak, partially melted
layer of the Earth’s mantle?
A. asthenosphere
B. core
C. lithosphere
D. oceanic crust
Do you agree or disagree?
4. The inside of Earth is mostly solid rock.
5. Rock makes up minerals.
6. Living things help make soil.