Restless Earth

Rock Cycleformation of different rock

This cycle is involved with three types of rocka. Sedimentary b. Metamorphicc. Igneous

schematicdiagramrock cycle

Restless Earth

Sedimentary Rocka. occurs near the Earth’s surfaceb. sediment settles to the bottom of the rivers, lakes, and oceans c. forms in layers called strata or stratification

Restless Earth

Sedimentary Rock Cycle

a. weather breaks down existing rock

b. deposition

c. compaction and cementation

Restless EarthMetamorphic Rock

a rock type that has changed into another type

a. occurs 2 to 16km deep in the Earthb. pressure is almost 4,000 times greater than at the surface c. temperature ranges from 1500C to 10000C

Restless Earth

Composition of Metamorphic rockheat and pressure play the significant rolesin forming this type of rock

Minerals + Heat and Pressure = New mineral

New minerals formed atdifferent temperaturesat different depths

Restless Earth

Igneous Rockformed from the cooling of magma

a. melted rock is trapped in the earth then coolsb. lava from a volcano erupts and then cools

Restless Earth

Three ways that rock can become magma

a. Temperatureb. Pressurec. Composition

Restless EarthIgneous Rock formations

Two process in which magma forms rock

1. Intrusive – coarse grained rock that developed after magma has cooled below the Earth’s surface

after weathering of Earth's surface, these intrusions are apparent

Shiprock, New Mexico

extinct volcano

dike

Devils Tower

Restless Earth

2. Extrusive rock – very small crystalline rock that is formed on the Earth’s surface called lava

or under the ocean’s surface, pillow lava

Restless Earth

Earth’s story

Two theories on the geologic processes which points to how the Earth’s landscape was/is formed

1. Uniformitarianism – James Hutton, 1795 developed the idea the landscape developed over long periods of time through a variety of slow geologic and geomorphic processes.

a. deep soil profiles were formed by the weathering of bedrock over thousands of years

b. slow uplift and subsidence of land surfaces cause changing topography

Restless Earth

2. Catastrophism - doctrine that the geological changes in the earth's crust have been caused by the sudden action of violent physical causes

a. biblical floodsb. asteroid impacts

Restless Earth

Relative dating (and I am not referring to my family tree)

uses the Principal of Superposition

a. It is based on sedimentary rocks and fossils b. Oldest layers are at the bottomc. Helps in the order of eventsd. Produces a geologic column

Restless Earth

Restless Earth

Restless Earth

The Geologic column can have some very interestingformations.

a. Faults - a crack in the earth's crust resulting from the displacement of one side with respect to the other

Restless Earth

b. Intrusion – molten rock that seeps into crevicesand cools

Restless Earth

c. Folding – rock layers bend and buckle frominternal forces

Restless Earth

d. Tilting – internal pressures slants the geologiccolumn without folding

Restless EarthUnconformity – a missing part of the geologic column

mostly occurs due to:a. depositionb. erosion

Three types of unconformitiesa. disconformity – rock layer is missing

Restless Earth

b. Nonconformity – sedimentary layer sits on topigneous or metamorphic rock

Restless Earth

c. Angular unconformity – layer between horizontallayer and tilted rock layer

Restless EarthAbsolute Dating

a process which establishes the age of an object

The process uses radioactive decay the decay works this way:

Unstable atoms turn into stable atoms

Parent isotope – unstable isotope

Daughter isotope – stable isotope

Restless EarthRadiometric dating

percentage of parent unstable isotope to daughter stable isotope

Uses half-life of isotope to date object

Three methods of radiometric datinga. Uranium-lead methodb. Potassium-argon methodc. Carbon-14 method

32

64

16

8

4

Restless Earth

The Earth may be described in two ways1. Composition2. Physical properties

Let’s take a look at each one 1. Composition - the Earth is composed

of three layersa. Crust – outermost layer b. Mantle – middle layerc. Inner and outer cores

Restless Earth

There are two categories of crusta. Continental – about 30 km thick; graniteb. Oceanic – about7 km thick; basalt

Restless Earth2. Physical propertiesa. Lithosphere – outermost layer (tectonic plates)

made up of 1. crust 2. upper part of mantle

b. Asthenosphere – soft part of mantlec. Mesosphere – strong part of mantle, extends

from asthenosphere to outer cored. Outer core – liquid layer of coree. Inner core – solid core

6 miles

60 miles

125 miles

400 miles

Restless EarthRock a little geology lesson!!!

Earth is made up of four layersa. inner core - mass of iron with a temperature of 70000 F b. outer core - electrical currents generated from this area produce the earth's magnetic field. c. mantle - slow moving molten rock or magma, 20000 F d. crust - layer from 4-25 miles thick consisting of sand and rock

Restless Earth

Mapping the Earth layersa seismograph can be used to measurethe thickness of each layer

Restless Earth

The lithosphere is made up of tectonic plates; theseare plates that float on the asthenosphere

Restless Earth

Cross section of a tectonic plate

Restless Earth

Continental DriftWegener, Alfred – 1880 - 1930

theory that all of the worlds land masses wereat one time together !!!!!

called the land mass Pangaea – about 245 million years ago

Evidence:a. continents fit together like a puzzleb. identical fossils on one continent are found on another

e.g. plants on S. America, Africa, Antarcticaand Australia

c. glaciers

Restless Earth

Restless Earth

Restless Earth

Restless EarthAre the continents on the move???

Yes, about 2 to 3 inches per year

How you ask...

Sea-floor Spreading!!!

As the continents move apart the mid-ocean ridgepulls apart and molten rock fills the gap

That is how the geologists determine the age of the ocean floor

Restless Earth

.

Restless Earth

As the magma makes new sea floor, the magnetic polesactually change directionAt irregular intervals, averaging about 200-thousand years, the Earth's magnetic field reverses. The end of a compass needle that today points to the north will instead point to the south after the next reversal.

Restless Earth

Theory of Tectonic Plates

Two possible answers for tectonic plate shift

a. gravityb. heat

Restless Earth

Restless Earth

Restless Earth

Restless Earth