Transcript Structure of the Earth - Mercer Island School District

Structure of the Earth
Compositional (Chemical) Layers
Crust: Low density
High in silicon (Si) and oxygen (O)
Moho: Density boundary between crust and
mantle
Mantle: Higher density
High in Magnesium (Mg) and Iron (Fe)
Core: High in Nickel (Ni) and Iron (Fe)
Earth: The Giant Magnet
Magnetic field created by liquid iron
convecting in outer core.
Magnetic field directs solar winds (ionized
particles) around the Earth or to the poles.
Aurora Borealis
Heat Flow in the Earth
Heat sources:
latent heat from the formation of the Earth
Radioactive decay in the core and mantle
Temperature at core: 3000-5000° C
Cooling processes:
Convection currents
Plate tectonics (volcanoes)
Mechanical (Physical) Layers of the Earth
Lithosphere: Crust and
upper, solid part of the
mantle; “plates” in plate
tectonics
Asthenosphere: Partially
molten part of mantle;
location of convection
current that drive plates
Outer core: Liquid
Inner core: Solid
Greatest temperatures, solid due to
intense pressure
Evidence for Structure of the Earth
Seismic (earthquake) waves
P waves (Primary): Longitudinal
(compressional) waves; faster, can move
through any matter
S waves (Secondary): Transverse waves.
Can only travel through solid matter.
Evidence for Structure of the Earth Cont.
S waves can not travel through the outer
core.
Rock Types
Igneous: Solidified molten magma
2 types of Igneous
Extrusive (volcanic) = erupted lava
Cools more quickly, so only small crystals
form.
Intrusive (plutonic) = never erupted magma
Cools more slowly within the earth, so larger
crystals can form.
Quartz= Silica (SiO2), light
color. Magma high in silica is
viscous.
High silica magma found in
more explosive volcanoes due
to build up of pressure with
more viscous magma.
Forms stratovolcano (cone
shape)
Low silica magma found in less
explosive volcanoes.
Form shield shape.
Extrusive Igneous Rock
Basalt
Andesite
Rhyolite
Low in silica
High in Silica
Black
Pale pink, grey
Intrusive Igneous Rock
Gabbro
Dacite
Granite
Low in Silica
High in Silica
Black
Pale Grey, pink
Sedimentary Rock
Sedimentary rock: formed by compaction of
sediments. Classified by particle size.
Shale
Sandstone
Sedimentary Rock cont.
Almost all fossils found in
sedimentary rock
Almost all fossil fuels (coal, oil,
gas) found in sedimentary
rock.
Metamorphic Rock
Metamorphic rock is
rocked that has been
changed by heat and/or
pressure.
Caused by burial and
proximity to volcanic
areas.
Dense, often streaks/folds
Many gemstones are
metamorphic.
Rock Cycle