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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.