Transcript Ltihosphere, atmosphere, hydrosphere

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
plates move together (may get
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
o
Sun provides energy for life, powers biogeochemical
cycles, and determines climate
• 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
Temperature Changes with Latitude
• Solar energy does not hit earth uniformly
– This is due to earth’s spherical shape and tilt
Equator (a)
High concentration
Little Reflection High
Temperature
Closer to Poles (c)
From (a) to (c)
In diagram below
Low concentration
Higher Reflection
Low Temperature
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
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%;
0.037%; trace amounts of other gasses
– Temperature decreases with altitude
CO2 =
• *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)
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
High
Low
– Left side of diagram
High
• Winds blow from high
to low pressure
Low
High
– Right side of diagram
Low
High
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
High
Low
High
Low
High
Low
High
Surface Winds: Westerlies
o
o
The Westerlies lie
between 30° - 60°
north and south
They blow from the
S.W. in the northern
hemisphere and N.W.
in the southern
hemisphere
Surface Winds: Polar Easterlies
o
o
The Polar Easterlies lie
between 60° - 90°
north and south
They blow from the
N.E. in the north pole
hemisphere and S.E. in
the 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
Westerlies
Trade winds
Position of Landmasses
Large landmasses in the
Northern Hemisphere
help to dictate ocean
currents and flow
Very little land in the
Southern Hemisphere
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