Earth Cycles By Diana L. Duckworth Rustburg High School Campbell 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 & harvest migration

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 a slow, steady march of loose material to 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 deep and 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 Principle Uniformitarianism 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 ROCKS cooling of molten rock material Sedimentary rocks deposition of weathered particles Metamorphic rocks changed by heat & pressure Surface processes burial Melting & cooling

NOT THE END...