Transcript Basic Mineralogy

Structure of the Earth
and Mineralogy
Environmental Science
Earth Science Unit
Questions for Today
1. What is the Structure of the Earth?
2. What are Minerals?
3. What are the physical and chemical
characteristics of Minerals?
4. What are Rocks?
5. How are Rocks Classified?
The History of the Planet
•
•
The Earth is the third planet out of the
“nine” planets in our solar system.
Two types of planets in our solar
system:
– Terrestrial (1st four)
– Jovian (Last “five”)
Interior Structure of the Earth
•
•
The Earth has a radius of about 6371
km, although it is about 22 km longer
at equator than at poles.
Density, (mass/volume), Temperature,
and Pressure increase with depth in
the Earth.
Interior Structure of the Earth
•
•
The Earth has a layered structure.
This layering can be viewed in two
different ways:
– Layers of different chemical composition
– Layers of different physical composition
Interior Structure of the Earth
•
Compositional Layering
– Crust - variable thickness and
composition
•
•
Continental 10 - 70 km thick
Oceanic 8 - 10 km thick
– Mantle - 3488 km thick, made up of a
rock called peridotite.
– Core - 2883 km radius, made up of
Iron (Fe) with some Nickel (Ni)
Interior Structure of the Earth
•
Layers of Differing Physical Properties
–
–
–
–
–
Lithosphere - about 100 km thick (up to 200 km
thick beneath continents), very brittle, easily
fractures at low temperature.
Asthenosphere - about 250 km thick - solid
rock, but soft and flows easily (ductile).
Mesosphere - about 2500 km thick, solid rock,
but still capable of flowing.
Outer Core - 2250 km thick, Fe and Ni, liquid
Inner core - 1230 km radius, Fe and Ni, solid
Minerals
•
•
Minerals are the building blocks of
Rock.
A mineral is:
–
–
–
–
Naturally Formed (It forms on its own!)
Solid
With a definite chemical Composition
A Characteristic Crystalline Structure
Examples of Minerals
•
•
Ice can be a mineral because of it’s
solid form, it’s definite chemical
Structure and crystalline structure
Halite is naturally formed salt.
Important Minerals in Earth’s
Crust
The Variety of Minerals we see depend on the
chemical elements available to form them.
In the Earth’s Crust the most abundant elements
are:
•
O, 45.2% by weight
•
Na, 2.3%
•
Si, 27.2%
•
K, 1.7%
•
Al, 8.0%
•
Ti, 0.9%
•
Fe, 5.8%
•
H, 0.14%
•
Ca, 5.1%
•
Mn, 0.1%
•
Mg, 2.8%
•
P, 0.1%
Minerals in the Earth’s Crust
•
•
•
Because of the limited number of
elements in the earth’s crust, there are
only about 3000 minerals known.
Only 20 to 30 of these are common
The most common minerals are based
on Si and O and are called Silicates.
Rocks
•
•
Rocks are aggregates of minerals that
are held together to form a
consolidated mass.
The three general types of Rock are:
– Igneous
– Sedimentary
– Metamorphic
Igneous Rocks
•
•
Igneous Rocks are rocks that result from a
melt – called magma.
There are two types of Igneous Rocks:
–
Plutonic Rocks – form beneath the earth’s
surface.
•
•
–
Coarse Textured
Ex: Granite and Gabbro
Volcanic Rocks – form above the earth’s
surface.
•
•
Fine textured
Ex: Rhyolite, Andesite, and Basalt
Sedimentary Rocks
•
Rocks that form near the surface of the Earth
through chemical precipitation from water or by
cementation of loose fragments (sediments)
Three types of Sedimentary Rocks:
•
–
–
Clastic – result from cementation of loose fragments.
Chemical - result from direct chemical precipitation from
surface water.
•
–
How Halite and Calcite is formed.
Biogeochemical – result from the chemical precipitation by
living organisms.
•
Limestone is the most common biogeochemical sedimentary
Rock.
Identifying Clastic Rocks
Name of
Particle
Size Range
Loose
Sediment
Consolidated
Rock
Boulder
> 256 mm
Gravel
Cobble
64-256 mm
Gravel
Conglomerate (if
clasts are
rounded) or
Breccia (if clasts
are angular)
Pebble
2-64 mm
Gravel
Sand
1/16 -2 mm
Sand
Sandstone
Silt
1/256 – 1/16
mm
Silt
Siltstone
Clay
<1/256 mm
Clay
Claystone,
mudstone, and
shale
Metamorphic Rocks
•
Rocks that result when any kind of
PRE-existing rock is buried deep in
the Earth and subjected to HIGH
temperature and pressures.
– Most metamorphic rocks show a banded
texture of the different sheets of silica
– Examples: Slate and Schist