Transcript Earth Cycles - Smyth County Schools

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
Condensation
evaporation
runoff
Precipitation
hibernation
Lives were ruled by cycles...
migration
http://animals.nationalgeographic.com/animals
Growth & harvest
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
uplift
erosion
Geologic cycle
transport
burial
deposition
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
ancient
Modern
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
Melting &
cooling
Surface processes
Metamorphic
rocks
Sedimentary
rocks
changed by heat & pressure
deposition of weathered
particles
burial
NOT THE END ...