Cycles of the Earth

Ch 18 Trefil & Hazen

The Sciences

All Matter above and beneath the

Earth’s surface moves in cycles.

What drives the earth cycles?

Sun radiates heat down on the ocean of air and water

Earth’s hot core or geothermal energy spreads upward

Demo and describe the water cycle

Water cycle constantly transfers the world’s water between three basic storage reservoirs.

• Oceans contain 97% of Earth’s water

• Of the 3% of the Earth’s freshwater:– 2.15% is locked away in glaciers and ice

sheets– 0.62% is groundwater, stored as soil moisture – 0.009% is in rivers and lakes– 0.001% is in the atmosphere

Amazingly, the whole shebang of water in lakes & rivers, water in rain & snow, water in our bathtub, shower, and drink bottles, amounts to only about 1% of the water in the world.

The Water (Hydrologic) Cycle

• p. 442• Ocean to Atmosphere

– 84% vapor from oceans; 16% from continents

• Atmosphere to Surface– Vapor cools, condenses & precipitates out in a week,

or few hours or few centuries; depends.– 77% precipitation falls on the oceans

• Surface to Ocean– 23% of precipitation in water cycle meets our needs

via “surface water” and “ground water.”

Major steps in the water cycle:

• Ocean to Atmosphere

• Atmosphere to Surface

• Surface to Ocean

How do the different types of

precipitation form? • Rain--Vapor condenses around aerosols

and falls from sky.

How do the different types of

precipitation form? • Snow—ice crystals that assemble

themselves as they fall through a cloud

How do the different types of

precipitation form? • Hail--large frozen rain formed in a giant

cloud of an intense thunderstorm.

How do the different types of

precipitation form? • Sleet--falling snow may partially melt and

then refreeze into a frozen raindrop.

Motion of the Ocean

Discuss the cause/effect dynamics of global ocean currents. link

Here’s a new perspective:

Explaining ocean motion: p. 441

• Great currents move the ocean, distributing heat and regulating climate across Earth.

• General scheme– Warm equatorial water swirls pole-ward and

circulates in vast ocean areas.– Cool water moves around the poles and flows

toward equator as continents allow passage.

Atmospheric Convection on the Rotating Earth p. 452

Trade Winds: easterlies at equator

In the tropics, winds prevail from E to W.

Air warmed new equator travels pole-ward but gradually cools and sinks. Earth’s rotation deflects surface winds

Atmospheric Convection on the Rotating Earth p. 452

Polar Easterlies: In the polar regions,

cold dense air sinks and moves away from poles.

Earth’s rotation deflects surface wind from East to West.

Atmospheric Convection on the Rotating Earth p. 452

Westerlies

Near 30o N & S latitude, Earth’s rotation moves air from West to East, as warm air moves to poles.

Many ongoing processes constantly

change Earth.

How do “rocks” “cycle” ?

Rock Cycle

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”

• Ch 18 pp. 464-465.

Try Discussion Questions 1-7,

And visit links on pacing guide:

Hydrologic cycle

Atmospheric cycle

Rock cycle