Earth Cycles

ByDiana L. Duckworth

Rustburg High SchoolCampbell County, VA

Cycles observed by early man ...

Some were easy, such as

Day & night

cycles of the seasons

spring

summer

WINTER

FALL

Hydrologic Cycle… and the rivers run to the sea, yet the sea is not full

evaporation

Condensation Precipitation

runoff

Lives were ruled by cycles...hibernation

Growth & harvestmigration

http://animals.nationalgeographic.com/animals

Cycles - old idea in 1789

• James Hutton - Scottish physician

• familiar with cycles – cycling of blood in the body – cycling of air in and out of the lungs

• liked to take long walks, hiking vacations

• naturalist - keen observer of nature

• good thinker - synthesizer

Hutton’s two contributions

• Uniformitarianism– the present is the key to the past

• Geologic Cycle– the neverending cycle of the wearing away of

the continents and the rebuilding of the continents

Solid rock becoming soil...

… called weathering

Loose particles eroded ...

and carried away (transported)...

By rivers on bottom

And in suspension

And by ice in glaciers

And wind...

And underground in caves...

… everywhere aslow, steady marchof loose materialto be deposited...

loose material dropped, that is deposited ...

In lake beds & flood plains

Along shoreline

And in ocean

…why are there mountains left?

• Two possibilities– earth is very young and the mountains just

haven’t been worn away– earth is old, and in some way, mountains are

renewed

• Saw processes of continents wearing down– by erosion, transport & deposition

• Must be a return part of the cycle – wearing away must be followed by renewal

Evidence of oceans at higher levels

Fossils - remains of life

Ripples in rocks

Many rocks showed evidence of heat & pressure in rocks at high elevations

Must have been buried deepand then uplifted

How could uplift have occurred?

Volcanoes create new land

Rock layers have been broken and one side lifted up

Many small shifts along faults during earthquakes...

Grand Tetons created over millions of years by many small movements on a fault at base of mountains.

weathering

erosion

transport

deposition

burial

uplift

Geologic cycle

Uniformitarian PrincipleUniformitarianism

Processes today are the same as processes in the past because the fundamental laws of the universe

do not change.

Two Examples of Uniformitarianism

Modern

ancient

Has this cycle of wearing away & building back up always been in effect?

Angular unconformity – rocks at bottom are tilted from mountain building and were eroded before others were deposited on top.

Yes!!!!

“I see no vestige of a beginning and no prospect of an end.”

Remember...• All processes occur all the time

– somewhere on the earth

• All processes are very slow

• Many are catastrophic and discontinuous, producing small changes– volcanic eruptions– movement on a fault– floods

• Many small changes add up to big changes

How old is the earth?

• very very very old (4.6 billion years!)– processes are slow - millimeters per century– evidence of many cycles of

• weathering, erosion, transport, deposition, burial and uplift

– many small changes over a long period can wear away mountains & create new ones

Rock Cycle occurs when processes of geologic cycle act on earth materials

IGNEOUS ROCKScooling of molten rock material

Sedimentary rocks deposition of weathered particles

Metamorphic rockschanged by heat & pressure

Surface processes

burial

Melting &cooling

NOT THE END ...