Transcript the geosphere - SCIENCE

THE GEOSPHERE
The geosphere
• Is made up of rocks and rocks are made
up of minerals
• Minerals are the building blocks of rocks
• Elements are the building blocks of
minerals
The geosphere is made up of rocks
and minerals
• Just eight elements account for 98% of
Earth’s mass.
FORMATION OF THE
GEOSPHERE
• Formation of the
elements by the collision
of the Sun
• Released of heat
(change from kinetic
energy to heat energy)
• More gravitational
attraction toward the
planet`s center
• Radioactive decay
Composition of the Earth
Earth`s layers
Earth`s layers
• Core: iron rich, dense
• Mantle: less dense, rocky
• Crust: even less dense, rocky. Composed
of lighter elements (Oxygen and Silicon)
Earth`s crust
Oxygen and silicon make up 75% of Earth’s
crust.
Minerals
• Is a naturally formed, inorganic
crystalline solid, composed of a
determinable and ordered arrangement
of atoms with specific chemical
composition
• It is not manufactured in laboratories
• Ordered in a geometric pattern
• Have a range of compositions
• It is not made up of organic compounds
(no Carbon involved neither living things)
Mineral properties
• Are classified by the
chemical composition
and the crystal
structure
• Identified by physical
properties
Crystal form
• Perfect geometric
forms
• Is an expression of
the ordely
arrangement of its
atoms
• Every mineral has a
unique combination
of composition and
crystal form
Crystal form
•Some minerals have the same composition
but different arrangement of their atoms
•Diamond and graphite are two examples
•Such minerals are called polymorphs.
With a different crystal structure, the minerals will
have different properties.
Crystal form
• Internal atomic arrangement
is determined by atom/ion
charge, size, and packing.
• The conditions in which the
crystal grows also affect
crystal form.
• Temperature, pressure,
space for growth
Mineral Properties: Hardness
• Hardness is the resistance of a mineral to
scratching.
• Hardness is dependent on the strength of
a mineral’s chemical bonds.
• Bond strength is determined by ionic
charge, atom (or ion) size, and packing.
• The Mohs Scale compares the hardness
of different minerals.
Mineral Properties: Hardness
Mineral Properties: Cleavage and
Fracture
Cleavage is the
property of a mineral
to break along planes
of weakness.
• Planes of weakness
are determined by
crystal structure and
bond strength.
Mineral Properties: fracture
Fracture occurs in
minerals where
bond strength is
generally the same
in all directions.
• Minerals that
fracture do not
exhibit cleavage.
Mineral Properties: Color
• Color is an obvious feature for many minerals,
but it is not reliable for mineral identification.
• Chemical impurities can change a mineral’s
color.
• A mineral may occur in many color variations or
be colorless.
Mineral Properties: Density
Density is the ratio of a mineral’s mass to its
volume.
In simple terms, it is how heavy a mineral feels for
its size (volume).
Classification of Rock-Forming
Minerals
There are two
classifications of
minerals:
—Silicate minerals
—Nonsilicate
minerals
Silicate minerals
make up more
than 90% of the
Earth’s crust.
Classification of Rock-Forming
Minerals
Silicate minerals are made up of silicon (Si)
and oxygen (O) atoms, along with other
elements (Al, Mg, Fe, Mn, and Ti).
Classification of Rock-Forming
Minerals
The Silicates are divided into
two groups:
• Ferromagnesian silicates
—Contain iron and/or
magnesium
—Tend to have high density and
are darkly colored
• Nonferromagnesian silicates
—No iron or magnesium
—Tend to have low density and
are light in color
Classification of Rock-Forming Minerals
Nonsilicate minerals make
up about 8% of Earth’s
crust.
• Carbonate minerals
• Calcite, dolomite
• Oxide minerals
• Ore minerals—hematite,
magnetite, chromite
• Sulfide minerals
• Ore minerals—pyrite, galena
Classification of Rock-Forming
Minerals
• Sulfate minerals
• Gypsum, anhydrate
• Native elements
• Gold, platinum, iron
The Formation of Minerals and
Rock
Minerals form by the process
of crystallization.
Crystallization is the formation
and growth of a solid from a
liquid or gas
Minerals crystallize from two
primary sources:
—Magma (molten rock)
—Water solutions
The Formation of Minerals and
Rock
Minerals crystallize systematically
based on their respective
melting points.
—The first minerals to crystallize
from a magma are those with the
highest melting point and the
lowest amount of silica.
—The last minerals to crystallize
from a magma are those with
lower melting points and higher
amounts of silica.
The Formation of Minerals and
Rock
Water solutions associated with later stages
of crystallization from magma account for
many important deposits.
• As water solutions become chemically
saturated, minerals precipitate
• For chemical sediments, solubility rather
than melting point determines which
minerals will form first
— Low-solubility minerals precipitate first.
— High-solubility minerals precipitate last.
Rock Types
A rock is an aggregate of minerals—a
physical mixture. The three categories of
rock reflect how they were formed:
• Igneous
Formed from cooling and crystallization of
magma or lava
Rock Types
• Sedimentary
Formed from preexisting rocks subjected to
weathering and erosion
Rock Types
• Metamorphic
Formed from preexisting rock transformed
by heat, pressure, or chemical fluids
Igneous rocks
• Igneous rocks are formed from the cooling and
crystallization of magma or lava.
• Role of heat: induce melting points
• Role of pressure: reduced pressure lowers the
melting temperature of rock
• Role of fluids: fluids (primarily water) cause rocks to
melt at lower temperatures.
Sedimentary rocks
Sedimentary rocks are products of 4
processes:
•
•
•
•
Weathering
Erosion
Deposition
Sedimentation
Sedimentary rocks
• Weathering—the physical
breakdown and chemical
alteration of rock at Earth’s
surface
• Two types of weathering:
—Mechanical weathering—
breaking and disintegration of
rocks into smaller pieces.
—Chemical weathering—chemical
decomposition and
transformation of rock into one or
more new compounds.
Sedimentary rocks
• Erosion—the physical removal of material
by mobile agents such as water, wind, ice,
or gravity.
• Erosion does not occur in place. It involves
movement.
Sedimentary rocks
• Deposition: the stage in
which eroded particles
come to rest. Larger
particles are the first to be
deposited. Smaller
particles are able to remain
with the flow. In this way,
sediments are sorted
according to size as they
are deposited.
Sedimentary rocks
• During sedimentation,
sediment particles are
deposited horizontally
layer by layer.
• As deposited sediment
accumulates, it
changes into
sedimentary rock.
Metamorphic Rocks
• Metamorphic rocks are
produced from:
—Igneous rocks
—Sedimentary rocks
—Other metamorphic rocks
• Metamorphism occurs via
recrystallization and
mechanical deformation.
The rock cycle
• Molten rock rises from the depths of Earth,
cools, solidifies, and eventually returns to
become magma again.