Unit 1“Physical & Chemical World”

Earth Layers/Tectonics/SoilsAtmosphere

Water

GEOLOGIC TIME SCALE• Organizes Earth’s 4.6

billion years of history into subgroups

• Subgroups:– Eons

• Eras– Periods

» Epochs

• 4 Major Eons…

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 1-10 cm/year• 15 major plates- We are on North American Plate

Plate Boundaries• Where 2 plates meet

• 3 types of plate boundaries

“Ring of Fire” – Pacific Ocean

Ring of Fire Video (short)

Hot Spot (Short)

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 (next 3 slides)

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: Himalayas- Indian 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

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

Tsunami

December 2004 – Sumatran Tsunami

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. Pinatubo- Philippines)

– 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

The Layered EarthMantle

• Made of less dense materials– Oxygen, magnesium, silicon

• Two regions:– Lower mantle - solid– Upper mantle or

athenosphere - plastic and movable

• Convection currents form in the athenosphere and are responsible for plate tectonics

No t to sc a le

To sc a le

A sthenosphe

Litho sp he re (c rust a nd up p e r- mo st so lid ma ntle )

Inne r c o re

O ute r c o re

M a ntle

C rust

So lid

Liq u id

C o re

M a ntle

C rust 0-100 km thic k

2,900 km

5,100 km

6,378 km

The Layered EarthCrust

• Also referred to as the lithosphere

• Composition is less dense than lower layers

• Skin of the physical planet• Two types:

– Oceanic - higher density; basalts– Continental - lower density;

granites

No t to sc a le

To sc a le

A sthenosphe

Litho sp he re (c rust a nd up p e r- mo st so lid ma ntle )

Inne r c o re

O ute r c o re

M a ntle

C rust

So lid

Liq u id

C o re

M a ntle

C rust 0-100 km thic k

2,900 km

5,100 km

6,378 km

Plate tectonics

• 7 major plates, many smaller plates• Moving relative to one another; average

speed of a few inches per year• 3 types of boundaries between plates:

– Convergent– Divergent– Transform-fault

Rock Types

Rock Cycle - Cycle of creation, destruction, and metamorphosis. Three major rock classifications:

Igneous

Sedimentary

Metamorphic

Igneous Rocks

Most common type of rock in earth’s crust. Solidified from magma extruded onto the surface

from volcanic vents.

Quick cooling of magma produces fine-grained rocks.

Basalt (makes up ocean floor)

Slow cooling of magma produces coarse-grained rocks.

Granite

Sedimentary Rock

Formed by deposited materials that remain in place long enough, or are covered with enough material for compaction, may again become rock.

Metamorphic Rock

Pre-existing rocks modified by heat, pressure, and chemical agents. Chemical reactions can alter both the

composition and structure of rocks as they are metamorphosed.

Marble (from limestone)

Quartzite (from sandstone)

Slate (from mudstone and shale)

Weathering

Mechanical - Physical break-up of rocks into smaller particles without a change in chemical composition.

Chemical - Selective removal or alteration of specific components that leads to weakening and disintegration of rock. Oxidation

Sedimentation - Deposition of loosened material.

EXPLANATIO N

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Geological Boundaries