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Unit 2: The Earth
Book: Chapter 14.1-2 Barron: Chapter 1 Test: October 17/18
September 26Put the list of topics in your binder (the handouts section)
Bellringer
Q: In what other area of APES can you relate convection currents? And how?
MA:
CA:
Soil lab is moved back a bit since we should talk about plate tectonics a little more so the two topics don’t run together
September 27“Civilization exists by geological consent, subject to change without notice.”
- Will Durant
Reflect on this quote. What does it mean?
MA:
CA:
September 28Turn in your lab if you didn’t yesterday.
Finally answer the guiding question:
What made Mt. Vesuvius erupt?
Use all of the following vocabulary words in your explanation - convectıon currents, tectonıc plates, asthenosphere, lıthosphere,
subductıon, and seafloor spreadıng.
P.s. Were you absent for the population quiz, test, or test corrections? Be sure to make them up by this Friday!
What made Mt. Vesuvius erupt?Differential heating in the asthenosphere (core is hotter than the crust) creates convection currents in the magma. This magma
causes the movement of the tectonic plates (the broken pieces of the cold lithosphere) via seafloor spreading. New magma bubbles up at rifts and ridges on the ocean floor that pushes old rock further from the ridge, while the other end of the plate is being subducted and begins the cycle again. At plate boundaries, we see volcanoes and
earthquakes due to the movement of the plates in different directions.
In the case of Mt. Vesuvius, the Eurasian plate is subducting under the African plate, melting the rock and causing it to bubble up and
explode as a volcano.
Geologic Time Scale- The organization of Earth’s past based on major geologic
and paleontological events. - Eons → Eras → Periods → Epochs → Stages - Key principles:
- Rock layers (strata) are laid down in succession - Principle of superposition - any given layer is probably
older than the one above it and younger than the one below it
Geologic Time Scale- 3 complications
- 1) layers can become eroded, distorted, tilted, or inverted
- 2) layers laid down at the same time in different areas can look differently
- 3) a layer only represents part of Earth’s history
Geologic Time Scale
4.5 bya 3.5 bya 1.5 bya 700 mya 400 mya
Earth cools Prokaryotes Eukaryotes Sea Land
No life Single celled life forms Multicellular Life forms
Now
Geologic Time Scale1. Precambrian
- Before 570 mya- Primitive marine life
Geologic Time Scale2. Paleozoic (570-225 mya)
- A. Cambrian (570-500 mya)- Abundant marine vertebrates, appearance of
primitive marine algae
Geologic Time Scale2. Paleozoic (570-225 mya)
- B. Ordovician (500-430 mya)- First vertebrates (fish), a lot of marine algae
Geologic Time Scale2. Paleozoic (570-225 mya)
- C. Silurian (430-413 mya)- Invasion of land by invertebrates and primitive
plants
Geologic Time Scale2. Paleozoic (570-225 mya)
- D. Devonian (413-350 mya)- Age of fishes
Geologic Time Scale2. Paleozoic (570-225 mya)
- E. Carboniferous (350-275 mya)- Age of amphibians- Formation of great coal swamps
Geologic Time Scale2. Paleozoic (570-225 mya)
- F. Permian (275-225 mya)- Expansion of reptiles
Geologic Time Scale2. Mesozoic (225-65 mya)
- A. Triassic (225-180 mya)- First birds
Geologic Time Scale2. Mesozoic (225-65 mya)
- B. Jurassic (180-135 mya)- AGE OF DINOSAURS
Geologic Time Scale2. Mesozoic (225-65 mya)
- C. Cretaceous (135-65 mya)- Dominance of land by conifers, first flowering
plants appear
Geologic Time Scale3. Cenozoic (65 mya-present day)
- A. Paleogene (65-2 mya)- Humans, dominance on land of mammals, birds,
insects, and flowering plants
Geologic Time Scale3. Cenozoic (65 mya-present day)
- B. Neogene (2 mya-present day)- Rise of civilizations, increase in number of herbs and
grasses- Important events - Ice Age
Earth Structure- Earth can be divided into
- Biosphere (all forms of life)- Hydrosphere (all forms of water)- Internal structures (crust, mantle, core)
Earth Structure- The Earth, like Shrek, has layers!
Crust- The cold brittle shell
- Floats on top of the mantle- Fractures easily
- Comes in 2 flavors - continental and oceanic
Continental Crust- Very thick (surface to 20-30 miles down)- Granite rich (silicon dioxide)- Stratified - Less dense
Rock StrataSee the different colored lines?
Oceanic Crust- Thinner (bottom of ocean floor to 6-7 miles down)- Basalt rich (iron, magnesium)- Very dense → subducts beneath
continental crust
Moho- Mohorovicic Boundary- Divides the crust and the
mantle- 3 miles below the ocean
floor and 19-31 miles below continental
Mantle- Most of earth’s mass- Fe, Al, Mg, silicon-oxide
Compounds- 1000oF (1000oC)- Top third is spongey and
plasticy, bottom is solid
Core- Mostly made of iron- Outer core
- molten- Inner core
- Solid due to pressure
What they’re made of
How they behave
Lithosphere- Solid outer part of Earth- Includes the crust and the upper rigid part of the mantle
Asthenosphere- Flowy plasticy part of the upper mantle- The “jelly” between 2 slices of bread (lithosphere and
mesosphere)
The Continental Drift Theory- Proposed in 1915 by Alfred Wegener
- Long time ago, there was one major landmass, called Pangea
- Since then, they have broken up into smaller pieces
What factors led to this conclusion?1. Fossilized tropical plants have been found beneath
Greenland’s icecaps
um...
What factors led to this conclusion?2. Glaciated landscapes occurred in the tropics of Africa and South America
What factors led to this conclusion?3. Tropical regions on some continents had polar climates in the past, based on paleoclimatic data
What factors led to this conclusion?4. The continents just look….like they fit together!
What factors led to this conclusion?5. Rocks in the east coast of North and South America were similar to the west coasts of Africa and Europe
What factors led to this conclusion?6. Fossils of extinct LAND animals were found on separate land masses
But without a mechanism...Wegener died in 1930 with the scientific community thinking he was a fool
The Seafloor Spreading Theory- Similar patterns of magnetic properties were found on
either side of mid-oceanic ridges - AND dating showed that as they moved away from the
ridge, the rocks got older- SO → new crust is created at volcanic
rift zones
Plate Tectonics - Movement of the lithosphere, which is broken into huge
sections called tectonic plates
Convection Currents- Rising of hot and sinking of cold cause the fluidy
asthenosphere to move the plates of the brittle lithosphere
Subduction Zones- Lithosphere is broken up into massive plates that float and
move on the viscous asthenosphere- A subduction zone is where 2 tectonic plates meet and
move toward each other, with one sliding underneath and moving into the mantle
Transform Boundaries- Plates slide past each other
San Andreas Fault- The Pacific & North American plates are moving
past each other, so soon (in like 50 million years)...part of California will be an island near Alaska!
Uh oh
Divergent Boundaries- When plates move apart from each other- As this happens, new crust is being generated- Examples: Oceanic → Mid-Atlantic Ridge, East Pacific
Rise; Continental → East African Great Rift Valley- Areas of frequent oceanic earthquakes
Not the same thing
Convergent Boundaries- When plates move toward one another and collide; forms
either a subduction zone (more dense plate moves under the less dense) or an orogonic belt (two plates collide and compress)
Convergent Boundaries → Ocean-Ocean- Form islands arcs (curved chain of volcanic islands)...
examples include Japan and the Aleutian Islands of Alaska
Convergent Boundaries → Ocean-Continentsubducts and creates an oceanic trench and a continental mountain range (example - Cascade Mountain Range)
Convergent Boundaries → Continent-Continent-
crumble up and rise, creating mountains (example - Himalayans)
Notice-Ring of Fire-Nazca Plate (O) → Andes Mountains (C)-Juan de Fuca (O) → Antarctic Plate (O) creating island arcs- Mid-Atlantic Ridge (Spreading Zone)- Red Sea is getting bigger
You should see lots of your earthquakes on these boundaries!
Consequences of Plate Movement- Volcanoes & Earthquakes
Volcanoes 95% occur at subduction zones and mid-oceanic ridges
Volcanoes - 5% at hot spots
(where the mantle is really close to the surface). Example is Hawaii.
Volcanoes
Produces ejecta, molten lava, and toxic gases
Volcanic Effect on Weather - They introduce large levels of sulfur dioxide, that become
sulfate in the atmosphere- Particles will settle out after 2 years, leading to acid rain
Volcanic Eruptions - Depends on the gases, amount of silica (viscosity), how free
the conduit is (does it flow or boom?)- Correlates with seismic activity- Produces new landforms and increased
soil nutrient levels
Volcanic Structure
Mount Saint Helens- Washington State, erupted in
1980- Removed trees, increased soil
erosion, destroyed wildlife, and increased pollution
- Also caused mudflows, melting of glacial ice and snow, and flooding
- Killed 57
Mount Pinatubo- Island of Luzon in the
Philippines- June 1991, erupted for 9 hours- Produced 18 million metric tons
of sulfur dioxide that encircled the entire stratosphere in 3 weeks
- Caused a 2oF cooldown after 3 years
Yellowstone Caldera- A supervolcano that last erupted 600,000 years ago, 100
times worse than Mt. Pinatubo, and...it could erupt at any time…
Earthquakes- Two pieces of rock are sliding
past one another, or one is moving up while the other is moving down
- Earthquakes occur when tension builds up between the 2 rocks and all of a sudden they snap (similar to stretching a rubber band and smacking someone with it)
Faults- A fracture in rock across which
there is movement
Fault Zone- Large expanses of rock
where movement has occurred
Epicenter vs Focus- Focus → the location where the rock ruptures- Epicenter → the exact
point on the surface of the earth above the focus- Calculated using the
data of at least 3 seismology locations
Richter Scale- How we measure earthquakes,
in terms of intensity, measuring the amplitudes of waves
- Logarithmic scale, increasing by a scale of 10- Example: a 7 is 10 times
greater than a 6
Seismic Waves - Body Waves- Body waves - S waves & P waves
- P waves travel through the earth, caused by expansion/contraction of bedrock
- S waves are produced when material moves vertically or horizontally, traveling along the uppermost layers of the earth
Seismic Waves - Surface Waves- Two types - body waves and surfaces
waves - Surface waves - the rolling or
swaying motion, slower than P or S waves. They cause ground motion and damage.
Severity of EarthquakesDepends on
- The amount of stored potential energy- The distance the rock mass moved when the energy was
released- How far below the surface the movement occurred- The makeup of the rock material
Severity of Earthquakes- Primary effects - damage to buildings and infrastructure,
loss of life and injury- Secondary effects - rock slides, flooding due to subsidence
of land, liquefaction of recent sediments, fire, and tsunamis
Haiti, 2010- 7.0, near the Caribbean plate
and North American plate- Affected 3 million people
(200,00 died, 250,000 seriously injured)
- Port-au-Prince and surrounding areas were completely destroyed due to inadequate building codes
San Andreas Fault- Extends 800 miles through
California to Baja California, Mexico, the tectonic boundary between the Pacific plate and North American plate
- 1906 - portion ruptured near San Francisco, causing 3,000 deaths from resulting fires
Tsunamis- Created when a body of water is rapidly displaced, usually
by a subduction zone related earthquake
Indonesia, 2004- A 9.3 earthquake in the Indian Ocean caused tsunamis that
killed 300,000 people
Stop at 2:10
Tohoku, 2011- 9.0 earthquake created a 23 foot tsunami- 15,839 dead and 3,647 missing- The cooling systems at the Fukushima
Nuclear Power Plant failed, resulting in a nuclear crisis
Plates move slowly over time and sink in areas of volcanic island chains, folded mountain belts, and trenches, and rise up from ridges and rift valleys.