oceans and atmosphere chapter 13 oceans, winds, waves, and coastlines geology today barbara w. murck...

Oceans and AtmosphereOceans and Atmosphere

Chapter 13

Oceans, Winds, Waves, and Coastlines

Geology Today

Barbara W. Murck

Brian J. Skinner

N. Lindsley-Griffin, 1999Earth from space. Equator crosses Africa through the green belt, Sahara desert is brown.

Earth’s AtmosphereEarth’s AtmosphereAtmosphere - the gaseous envelope that surrounds a planet or other celestial body.

Air is the gaseous envelope that surrounds the Earth.

Aerosols - small liquid or solid particles suspended in the air (fog, smoke)

Humidity - amount of water vapor in air.

N. Lindsley-Griffin, 1999

Shuttle view across east end of Mediterranean Sea, NE Africa and the Mideast

(Fig. 13.1, p. 369)

Earth’s AtmosphereEarth’s Atmosphere

Nitrogen and oxygen are the two most abundant gases in the atmosphere. (Fig. 13.2, p. 369)

N. Lindsley-Griffin, 1999

Earth’sAtmosphere

Earth’sAtmosphere

N. Lindsley-Griffin, 1999

The atmosphere is divided into 4 temperature zones divided by pauses, levels where temperature changes greatly.

Fig. 13.3, p. 370

N. Lindsley-Griffin, 1999

80% of atmosphere’s mass Source of most weather

Contains greenhouse gases that trap heat to warm Earth’s surface

The TroposphereThe Troposphere

Greenhouse EffectGreenhouse Effect

N. Lindsley-Griffin, 1999

1) Solar rays enter as short- wavelength radiation.

2) 30% reflected back by clouds; 70% absorbed as heat.

3) Heat energy is radiated back into space as long-wavelength infrared energy.

4) Greenhouse gases absorb radiated heat, slow down its escape, help to heat air and planet’s surface.

(Fig. 13.4, p. 371)

Ultraviolet Radiation Protection

Ultraviolet Radiation Protection

N. Lindsley-Griffin, 1999

Error in Fig. 13.5 (p. 372):

Thermosphere absorbs short wavelengths

Mesosphere absorbs intermediate wavelengths

Stratosphere absorbs long wavelengths

Ozone layer (O3) in stratosphere

Fig. 13.5, p. 372

Global Atmospheric CirculationGlobal Atmospheric Circulation

Sun’s heat and Earth’s rotation cause oceans and air to circulate.

Surface heats more where Sun’s rays are perpendicular…

less where rays are at angle to the surface.

Warmer air/water flows towards colder areas

N. Lindsley-Griffin, 1999 Fig. 13.6, p. 373

N. Lindsley-Griffin, 1999

Uneven heating creates huge convection cells in the atmosphere as hot air rises.

Convergence = trade winds

Equator - rising hot air, low P

air cools along top of cell

Subtropics - cool air sinks, hi P

air warms along bottom of cell

Polar front - warm moist air rises, low Pressure

Poles - cold dry air descends, high

Pressure

Global CirculationGlobal Circulation (Fig. 13.7, p. 374)

N. Lindsley-Griffin, 1999

Coriolis Force - tendency of free-floating things (air, water) to veer off course.

Causes the rising equatorial air to move at an angle instead of directly towards poles.

Atmospheric and ocean currents are both affected by: Coriolis Force

arrangement of continents and oceans.

(Fig. 13.7, p. 374)

Global CirculationGlobal Circulation

Global Climate ZonesGlobal Climate Zones

N. Lindsley-Griffin, 1999

Climate zones are controlled by air and ocean circulation patterns: rainforests form where rising warm air cools off and loses its moisture, deserts where dry air descends to surface.

(Fig. 13.8, p. 375)

Weather - local atmospheric conditions at any particular time

Climate - weather patterns averaged over a long period of time

“Typical weather” is a myth - weather actually fluctuates between extremes whose mean or average is “climate”

Climate vs. WeatherClimate vs. Weather

N. Lindsley-Griffin, 1999

Monsoons = Seasonally reversing winds:

Winter winds blow from high cold central Asian plateau - dry because cold air holds little moisture, and there is no source.

Summer winds blow from warm moist Indian Ocean - heavy rains and hot humid weather.

(Fig. 13.9, p. 377)

MonsoonsMonsoons

N. Lindsley-Griffin, 1999

Oldest rocks on Earth are about 4.0 b.y. old, gneisses that were once sedimentary strata. Therefore, liquid water covered much of the Earth foe at least 4.0 b.y.

- Probably condensed from steam during volcanic eruptions

Earth’s OceansEarth’s Oceans

N. Lindsley-Griffin, 1999

Review - Ocean floor features

(Fig. 4.2, p. 90)

Earth’s OceansEarth’s Oceans

N. Lindsley-Griffin, 1999

Surface Layer - About 100 m deep

Relatively warm low-density water

Major life-zone of the sea

Major Ocean Layers

Major Ocean Layers

N. Lindsley-Griffin, 1999

Fig. 13.10, p. 379

View looking west along the equator

Thermocline - water temperature decreases rapidly as depth increases (Figure caption wrong in book)

Deep zone - water is uniformly cold (2 C), dense

Note that both reach surface near poles

Major Ocean Layers

Major Ocean Layers

N. Lindsley-Griffin, 1999

Fig. 13.10, p. 379

View looking west along the equator

Surface CurrentsSurface

Currents

N. Lindsley-Griffin, 1999

Surface currents curve CW in No. hemisphere, CCW in So. hemisphere

Deep ocean currents begin in Polar regions where cold dense water sinks and spreads slowly outward. Saline because of sea

ice formation which removes fresh water from ocean.

Deep Ocean CurrentsDeep Ocean Currents

N. Lindsley-Griffin, 1999

Fig. 13.12, p. 381

The cold dense water gradually wells up, becoming warmer and less saline at shallower levels. Cycle = 1000 yrs.

N. Lindsley-Griffin, 1999

Fig. 13.12, p. 381

Deep Ocean CurrentsDeep Ocean Currents

NormalNormal years: 1) Cool deep water upwells off Peru.

2) Tradewinds and warm currents move east to west.

3) A warm water pool forms in the western Pacific, causing moist air to rise and cool off.

4) Cooling initiates precipitation and abundant rain falls on Indonesia.

(Fig. B13.1, p. 383)

El NinoEl Nino

N. Lindsley-Griffin, 1999

1

2

3

4

El Nino years: 1) Tradewinds slacken and warm water moves to central Pacific.

2) Air currents reverse; cool, dry air descends over Indonesia, bringing drought.

3) Rising moist air over the warm water pool increases precipitation over the central Pacific.

4) Eastern Pacific water warms up, downwelling shuts off nutrient supply, kills fish.

(Fig. B13.1, p. 383)

El NinoEl Nino

N. Lindsley-Griffin, 1999

1

2

2

3

4

Tides - the cycle of regular rise and fall of water level in large bodies of water.

Result from gravitational interaction of the Moon, the Sun, and Earth, together with inertia of the Earth-Moon system.

TidesTides

N. Lindsley-Griffin, 1999

On the side facing the Moon, gravity distorts water into a tidal bulge.

On the opposite side, inertial forces are greater than pull of Moon’s gravity and a bulge forms in the other direction.

Bulges remain stationary while Earth rotates through each.

TidesTides

N. Lindsley-Griffin, 1999

Fig. 13.13, p. 384

TidesTides

Targant & Lutgens, J.R. Griffin, N. Lindsley-Griffin, 1999

Spring Tides -- maximum range

Twice monthly

Earth, Moon, and Sun aligned

Sun adds slight pull.

Neap Tides -- minimal range

Twice monthly

Sun 90 degrees away from Earth-Moon, counteracts their influence

TidesTides

N. Lindsley-Griffin, 1999

Bay of Fundy, Nova Scotia

Has some of the largest tidal ranges in the world

- Because bay narrows towards its tip, forcing tidal waters to constrict and build up higher.

Tidal Bore - An actual wave moves up the bay at the front of the advancing tide.