Lithosphere, atmosphere, hydrosphere

Unit 2 A

Our Earth:Geologic Timescale

• The geologic time scale is a chronologic schema (or idealized model) relating to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth.

Geologic Timescale

• The table of geologic time spans presented here agrees with the dates and nomenclature proposed by the International Commission on Stratigraphy, and uses the standard color codes of the United States Geological Survey.

Geologic Timescale

• Evidence from radiometric dating indicates that the Earth is about 4.570 billion years old. The geological or deep time of Earth's past has been organized into various units according to events which took place in each period.

Internal Planetary Processes

• Layers of the earth– Lithosphere• Outermost rigid rock layer composed of plates

– Asthenosphere• Lower mantle comprised of hot soft rock

• Plate Tectonics- study of the processes by which the lithospheric plates move over the asthenosphere

• Plate Boundary- where 2 plates meet– Common site of earthquakes and volcanoes

Plates and Plate Boundaries

Types of Plate Boundaries

• Divergent Plate Boundary-2 plates move apart

o Convergent Plate Boundary-2 Convergent Plate Boundary-2 plates move together (may get plates move together (may get subduction)subduction)

Types of Plate Boundaries

• Transform Plate Boundary- 2 plates move horizontally in opposite, parallel directions

Earthquakes

• Caused by the release of accumulated energy as rocks in the lithosphere suddenly shift or break– Occur along faults– Energy released as seismic wave

• Focus- the site where the earthquake originates below the surface

• Epicenter- located on the earth’s surface, directly above the focus

• Richter scale and the moment magnitude scales are used to measure the magnitude

Tsunami

• Giant undersea wave caused by an earthquake, volcanic eruption or landslide– Travel > 450mph

• Tsunami wave may be 1m deep in ocean– Becomes 30.5m high on shore

• Magnitude 9.3 earthquake in Indian Ocean– Triggered tsunami that killed over 230,000 people

in South Asia and Africa

Solar Radiation

• 69% of incoming solar radiation is absorbed by atmosphere and earth– Remainder is reflected

• Albedo– The reflectance of solar energy

off earth’s surface– Dark colors = low albedo

• Forests and ocean– Light colors = high albedo

• Ice caps• Also see envirobrief pg 113

o Sun provides energy for life, powers biogeochemical Sun provides energy for life, powers biogeochemical cycles, and determines climatecycles, and determines climate

Temperature Changes with Latitude

• Solar energy does not hit earth uniformly– This is due to earth’s spherical shape and tilt

Equator (a)Equator (a)

High concentration High concentration Little Reflection High Little Reflection High TemperatureTemperature

Closer to Poles (c)Closer to Poles (c)

Low concentration Low concentration Higher Reflection Higher Reflection Low TemperatureLow Temperature

From (a) to (c)From (a) to (c)

In diagram belowIn diagram below

Temperature Changes with Season• Seasons are

determined by earth’s tilt (23.5°)

• Causes each hemisphere to tilt toward the sun for half the year

o Northern Hemisphere tilts towards the sun from Northern Hemisphere tilts towards the sun from March 21- September 22 (warm season)March 21- September 22 (warm season)

The Atmosphere• Invisible layer of gases that envelopes

earth • (ex. if earth were a hard-boiled egg, then the atmosphere

would be the thin membrane right under the shell)

• Content– 21% Oxygen– 78% Nitrogen– 1% Argon, Carbon dioxide, Neon and Helium

• Density decreases with distance from earth

• Shields earth from high energy radiation

Atmospheric Layers• Troposphere (0-10km)

– The “WEATHER MAKER”– 75-80% of the mass of the earth’s air found here– 78% nitrogen, 21% oxygen

• Minor components – H2O = 0.01% (poles) – 4% (tropics); Ar = 1%; CO2 = 0.037%; trace

amounts of other gasses – Temperature decreases with altitude

• *Stratosphere (10-45km)*• Similar composition as troposphere but less volume

– Less H2O and more ozone O3

– Temperature increases with altitude- very stable• Stratospheric ozone produced when O2 interacts with UV radiation and

forms O3

• “Global sunscreen,” ozone keeps 95% of UV radiation from reaching surface

• Mesosphere (45-80km)– Temperature decreases with altitude

Atmospheric Layers• Mesosphere (45-80km)

– The mesosphere extends from 50 to 80km in altitude with very sparse atmosphere, accounting for only about 0.1 percent of the mass of the atmosphere as a whole.

Atmospheric Layers

• Thermosphere (80-500km)– Gases in thin air absorb x-rays and

short-wave UV radiation = very hot

– Source of aurora

• Exosphere (500km and up)– Outermost layer– Atmosphere continues to thin

until converges with interplanetary space

Atmospheric Circulation

• Near Equator “Hadley Cells”– Warm air rises, cools and

splits to flow towards the poles

– ~30°N&S sinks back to surface– Air moves along surface back

towards equator

• This occurs at higher latitudes as well– Moves heat from equator to

the poles

Surface Winds• Large winds due in

part to pressures caused by global circulation of air– Left side of diagram

• Winds blow from high to low pressure– Right side of diagram

LowLow

LowLow

LowLow

HighHigh

HighHigh

HighHigh

HighHigh

Surface Winds: Trade Winds• The trade winds (also

called trades) are the prevailing pattern of easterly surface winds found in the tropics near the Earth's equator 0 °-30 ° north and south

• Blow from N.E. in the northern hemisphereand S.E. in the southern hemisphere

LowLow

LowLow

LowLow

HighHigh

HighHigh

HighHigh

HighHigh

Surface Winds: Westerlieso The The WesterliesWesterlies lie lie

between 30° - 60° between 30° - 60° north and southnorth and south

o They blow from the They blow from the S.W. in the northern S.W. in the northern hemisphere and N.W. hemisphere and N.W. in the southern in the southern hemispherehemisphere

Surface Winds: Polar Easterlieso The Polar Easterlies lie The Polar Easterlies lie

between 60° - 90° between 60° - 90° north and southnorth and south

o They blow from the They blow from the N.E. in the north pole N.E. in the north pole hemisphere and S.E. in hemisphere and S.E. in the south polethe south pole

Coriolis Effect

• Earth’s rotation influences direction of wind– Earth rotates from East to West– Deflects wind from straight-line path

• Coriolis Effect– Influence of the earth’s rotation on movement of

air and fluids– Turns them Right in the Northern Hemisphere– Turns them Left in the Southern Hemisphere

Coriolis Effect

• Visualize it as a Merry-Go-Round (see below)

Global Ocean Circulation

• Prevailing winds produce ocean currents and generate gyres

• Example: the North Atlantic Ocean– Trade winds blow west– Westerlies blow east– Creates a clockwise gyre in the North Atlantic

• Circular pattern influenced by coriolis effect

Global Ocean Circulation

Trade windsTrade winds

WesterliesWesterlies

Position of Landmasses

Very little land in the Very little land in the Southern HemisphereSouthern Hemisphere

Large landmasses in the Large landmasses in the Northern Hemisphere Northern Hemisphere help to dictate ocean help to dictate ocean currents and flowcurrents and flow

Vertical Mixing of Ocean waters account for deep (cold) and

shallow (warm) currents

Ocean Interaction with Atmosphere- ENSO

• El Niño-Southern Oscillation (ENSO)– Def: periodic large scale warming of surface waters of tropical

eastern Pacific Ocean

• Alters ocean and atmospheric circulation patterns• Normal conditions- westward blowing tradewinds keep

warmest water in western Pacific• ENSO conditions- trade winds weaken and warm water

expands eastward to South America– Big effect on fishing industry off South America

ENSO Climate Patterns

The white areas off the tropical coasts of South and North America indicate the pool of warm water.

Weather and Climate (defined)

• Weather– The conditions in the atmosphere at a given place

and time– Temperature, precipitation, cloudiness, etc.

• Climate– The average weather conditions that occur in a

place over a period of years– 2 most important factors: temperature and

precipitation– Earth has many climates

Land Masses can affect Weather: Ex. Rain Shadows

• Mountains force humid air to rise• Air cools with altitude, clouds form and

precipitation occurs (windward side)• Dry air mass moves down opposite leeward

side of mountain

Severe Weather: Tornadoes

• Powerful funnel of air associated with a severe thunderstorm

• Formation– Mass of cool dry air collides with warm humid air– Produces a strong updraft of spinning air under a

cloud– Spinning funnel becomes tornado when it descends

from cloud

• Wind velocity= up to 300mph• Width ranges from 1m to 3.2km

Severe Weather Tropical Cyclone (a.k.a. Hurricanes)

• Giant rotating tropical storms• Wind >119km per hour• Formation

– Strong winds pick up moisture over warm surface waters – Starts to spin due to Earth’s rotation– Spin causes upward spiral of clouds

• Damaging on land– High winds– Storm surges