0004 Earth Characteristics and Processes: 1. demonstrate knowledge of the earth's structure and composition.

Basic Structure of the Earth

• 8,000 miles in diameter

• lithosphere, hydrosphere, atmosphere

• 4 spherical regions:– crust, mantle, outer core, inner core

Earth Structure

0004 Earth Characteristics and Processes: 2. classify rocks and minerals based on their process of formation and characteristics.

What are Rocks? What are Minerals?

• Rocks• An aggregate or

mixture of minerals.• Composition can vary • Most rocks are

composed of more than one mineral

• Minerals• building blocks of

rocks; elements or compounds found in the Earth’s crust.

• > 3000 minerals differing in properties

link

Rocks

• Igneous = formed by the cooling and crystallization of magma (melted rock)

• Sedimentary = formed from accumulation of weathered material (sediments)

• Metamorphic = formed from preexisting rocks that have been transformed (changed)

Igneous, Sedimentary, Metamorphic

    Each type of rock records a different complex past.

    Each type of rock can be changed from one form to another and back again.

geologists call these transformations the “rock cycle”

Rock Cycle

Crystal Form

• Pyrite, Fe2S • Quartz, SiO2

Moh’s Hardness Scale

• 1.Talc

• 2.Gypsum

• 3.Clacite

• 4.Fluorite

• 5.Apatite

• 6.Orthoclase

• 7.Quartz

• 8.Topaz

• 9.Corundum • 10.Diamond

Cleavage & Fracture

Physical Properties of Minerals

• Crystal form

• Hardness

• Plane of Cleavage

• Luster

• Color and Streak

• Specific Gravity

Igneous Rock

  formed by cooling & crystallization

of magma.

   means “formed by fire”

  make up about 95% of the earth’s crust

 basalt (ocean floor) and granite (continents) are common examples

Sedimentary Rock

  formed from the weathered material carried by water, wind, or ice

  most common rocks in the upper crust

  cover over 2/3 of the earth’s surface

  sandstone, shale, and limestone

Metamorphic Rock

• ---formed from preexisting rocks (igneous, sedimentary, or other metamorphic)

• ----metamorphic means “changing in form”

• ----marble and slate are common examples

0004 Earth Characteristics and Processes: 3. identify the characteristics of soil and analyze how it forms.

0004 Earth Characteristics and Processes: 4. analyze constructive and destructive processes that form and change major geological features (e.g., tectonic movements, erosion, deposition).

0004 Earth Characteristics and Processes: 5. demonstrate knowledge of the theory of plate tectonics and evidence that supports the theory.

October 17, 1989

May 18, 1980

Earthquakes and volcanoes: evidence that our planet is not at rest.

• global distribution of earthquakes and volcanic centers…above crustal plate boundaries

• The surface of the earth is constantly changing and no feature on earth is permanent.

Why is the Earth so restless?

• “Convection Conveyer-belt”

• The heat that drives the motion of the mantle comes from two sources:

---Radioactive decay of materials in the mantle

---Heat left over from the formation of the earth

James Hutton 1726-1797

• "catastrophism," earthly changes were sudden & caused by a series of catastrophes

• This belief prevailed until the 1700s

• "uniformitarianism • 1785 James Hutton• The present is the key

to the past

Uniformitarian Principle

• the geologic forces and processes -- gradual as well as catastrophic -- acting on the Earth today are the same as those that have acted in the geologic past.

Alfred Wegener 1880-1930

Theory of Continental Drift

• (Wegener, 1915)

• continents plowed through crust of ocean basins, which would explain why the outlines of many coastlines(like South America and Africa) look like they fit together like a puzzle

Continental Drift: a theory ahead of its time

• impossible for a large mass of solid rock to plow through the ocean floor without breaking up

• mid 20th Century, new evidence from ocean floor exploration rekindled interest in Wegener's theory, ultimately leading to theory of plate tectonics.

Plate Tectonics: A modern version of

Wegener’s old idea • the outer rigid lithosphere consists of about

20 rigid segments called plates

• Most plates contain both continental and oceanic crust—a major departure from the continental drift theory

• The word tectonics comes from the Greek root "to build."

Folding and Faulting

• Compressive forces from moving plates can cause rock to bend & wrinkle into wavelike folds

• The crack or break in the rock is called a fault and the movement of the rock is “faulting”

Earthquakes

• Great forces of stress occurs as plates of rock pushed in opposite directions

• sudden movement as the blocks slide and then come to rest in a new position that eases the pressure

The entire San Andreas fault system is more than 800 miles long and extends to depths of at least 10miles within the Earth. In detail, the fault is a complex zone of crushed and broken rock from a few hundred feet to a mile wide.

Seismograph

• Richter Scale based on the amount of seismographic movement

• An earthquake with a number of 2 is just strong enough to be felt, 5 can cause much damage, 7 or more is classified as a major earthquake

Plate Boundaries

• 3 Main Types–Divergent

–Convergent

–Transform

Divergent Plate Boundaries

• plates are being pulled apart

• sea floor spreading at Mid-Atlantic Ridge

• Eurasia and North America are separating at a rate of about 5 cm per year

• East African Rift Valley

Convergent Plate Boundaries

• two plates are coming together

• 3 associated surface feature– deep ocean trench and chain of volcanic

islands – folded mountains – ocean plate subduction beneath continent

Transform Plate Boundaries

• one plate scrapes past the other

• San Andreas fault in California

• No mountain building or volcanism is associated with transform boundaries.

0004 Earth Characteristics and Processes: 6. recognize characteristics of fossils and how they show evidence of the changing surface and climate of the earth.