Download earth`s components & characteristics

EARTH’S
COMPONENTS &
CHARACTERISTICS
UNIT 9 Environmental
Geology
APES
GEOLOGIC TIME SCALE
• Organizes Earth’s 4.6
billion years of history
into subgroups
• Subgroups:
– Eons
• Eras
– Periods
» Epochs
• 4 Major Eons…
1. Hadean Eon
• Oldest amount of time
• 4.6-3.8 billion years
ago
• No rocks from this
eon found on Earth
• Evidence from
meteorites & moon
rocks
2. Archean Eon
• 3.8-2.5 billion years
ago
• 3.8 BYA Oldest rocks
on Earth
• 3.5 BYA oldest fossils
of cells (prokaryotes)
• 2.7 BYA atmospheric
O2 begins to rise
3. Proterozoic Eon
• 2.5 billion – 543
million years ago.
• 2.2 BYA oldest fossils
eukaryotic cells
• 600 MYA diverse
algae & soft
• Bodied invertes
4. Phanerozoic Eon
• 543 million years- present
• Paleozoic Era
– 543-248 million years
– Diverse land plants,
amphibians, reptiles, insects
(Cambrian Explosion)
– Mass extinction due to
glaciation (global cooling)killed 90% of species (end of
Permian period)
• Mesozoic Era
– 248-66 million years
– Age of Reptiles
– Mass extinction due to climate
change- 10-15% extinct
(Cretaceous extinctions)
• Cenozoic Era
– 65 million years to present
– Age of Mammals
STRUCTURE OF THE EARTH
• Planetary
differentiation- as
more dense materials
sank to center of
earth, less dense
material rose to
surface
•
Layers of Earth
• Core- center, mostly iron
– Inner core- 1220 km thick, T & P
cause iron to solidify
– Outer core- 3480 km thick, liquid
iron, creates magnetic field
• Mantle- 70% of earth’s interior,
made of O, Si, Mg
– Asthenospere- closest to core,
gelatinous, where magma is
formed
– Upper mantle- cooler, more solid,
brittle
• Crust- outermost layer
– Crust + upper mantle make up
lithosphere
Plate Tectonics
• Tectonic plates- made of…
– Uppermost mantle
– Crust- 2 types:
• Oceanic- thin (5-10 km),
dense, rich in Fe, Mg, Si,
below sea level
• Continental- thick (20-70 km),
less dense, rich in Ca, Na, K,
Al
• Constantly moving about 110 cm/year
• 15 major plates- We are on
North American Plate
Plate Boundaries
• Where 2 plates meet
• 3 types of plate
boundaries
1. Transform
Boundaries
• Plates slide past each
other at transform faults
• Movement is horizontal
(strike-slip fault)
– To the left- sinistral
– To the right- dextral
• Mostly smooth movement
• If stuck, pressure builds,
causes earthquakes
2. Convergent Boundaries
• 2 plates move toward
each other
• 3 types:
a. OCEANIC - CONTINENTAL
•
•
•
•
•
Oceanic plate is forced
under continental plate
Called subduction
Creates deep-sea
trench
Creates volcanic
mountains along
continental plate.
EX: Peru-Chile Trench
and Andes Mountains of
South America
b. OCEANIC - OCEANIC
•
•
•
•
•
•
Oceanic plate is forced
under another oceanic
plate
Called subduction
Crust melts into mantle
Creates deep-sea trench
Creates arc of volcanic
islands that parallel trench
EX: Mariana Trench &
Mariana Islands
Aleutian Trench & Aleutian
Islands
c.CONTINENTAL - CONTINENTAL
• Two continental
plates collide
• Mountain ranges are
created
• EX: HimalayasIndian plate forced
under Eurasian plate
3. Divergent Boundaries
• 2 plates move apart
• Creates rifts
• Magma comes to surface
& cools, creating crust
• Usually in oceans, but
can occur in continents
(Africa’s Rift Valley)
• Creates mid-ocean ridges
• EX: Mid-Atlantic Ridge
created when N.American
plate pulls away from
Eurasian plate.
CAUSES OF PLATE
MOVEMENT
• Convection currents
– Hot mantle rises
– Cools down
– Cooled-down mantle
sinks
– Creates currents that
move plates.
THEORY OF CONTINENTAL
DRIFT
• Alfred Wegner was first to
propose theory of
continental drift
• He said:
– All continents joined in
large land mass called
Pangea (Greek for “all
land”)
– Pangea began breaking up
200 million years ago.
– Continents ended up where
they are now
– Continents are still moving
Evidence of Continental Drift
• Fossils- similar plants &
animals on widely
separated continents
• Rock Formations- similar
rock types & stratification
between 2 continents
• Climate- Antarctica has
coal deposits, indicating it
had swamps, thus
warmer weather= closer
to equator
Geologic Hazards associated with
Continental Drift
•
•
•
•
Earthquakes
Volcanoes
Landslides
Floods
Earthquakes
• Epicenter- point where first
movement occurs
• Damage depends on soil
underneath
• Modern contractors build
weak spots, pads/floats to
absorb vibration
• Underwater earthquakes
cause tsunamis
– Destroy coastal ecosystems
– Saltwater infiltrates soil
– sewage/industrial waste infect
freshwater supplies
Volcanoes
• Good
– Created land (fertile soil),
atmosphere, oceans
• Bad
– Release sulfur, combines with
H20 to form sulfuric acid;
interferes with solar radiation,
cools climate (Mt. PinatuboPhilippines)
– Dust/Ash- can change climate
by blocking sunlight (1815- Mt.
Tambora in Indonesia,
snowed in July in parts of New
England, “year without a
summer”)
– Clouds of hot, toxic gases
– Mudslides
Landslides
• Mass
wasting/movement
• Usually slow & subtle,
can happen all at
once
• Construction, forest
clearing, agriculture,
building on steep
slopes increase
frequency & damage
Flooding
• Excess water that
overflows stream banks
• Contaminates everythingvery costly
• Pavement/buildingsspeeds rate of runoff, soil
has no chance to absorb
• Floodplains- fertile, attract
people/agriculture,
affected most by flooding
• READ chapter 16 on
Natural Disasters!!