Download Plate tectonics, tsunamis, volcanoes, and seasons

Plate tectonics, tsunamis,
volcanoes, and seasons
BY GINNY BISTER
Earth structure
 Earth can be divided into
3 sections: the biosphere,
the hydrosphere, and the
internal structure



Biosphere: includes all
forms of life
Hydrosphere: includes all
forms of water
Internal structure:
includes crust, mantle,
and core
Plate tectonics
 Theory rose from two separate geological observations:
continental drift and seafloor spreading
 Continental drift theory
 Alfred Wegener proposed that all present day continents were
once one landmass (Pangaea)
 theory was based on 5 factors
1.
2.
3.
4.
5.
Fossilized plants discovered beneath Greenland's ice caps
There were glaciers in africa and south America
The continents fit together like a puzzle
Similarities existed in rocks on the east costs of the Americas and on
the west coasts of africa and Europe
Present day tropical regions once had polar climates
 Seafloor spreading theory
 During the 1960’s alternating patterns of magnetic properties were
discovered in rocks on the seafloor as well as mid-oceanic ridges
 Dating of the rocks suggests that as a rock moved away from the ridge, it
got older
 This suggested that new crust was being created at volcanic rift zones
Plate tectonics (cont.)
 Transform boundaries
 Plates slide past each other
 The friction and stress buildup causes earthquakes
 Convergent boundaries
 When two plates slide toward each other
 Can form a subduction zone or an autogenic belt (of
two plates collide and compress)
 Divergent boundaries
 When two plates slide apart from each other
 The space created is filled with magma
 Can create massive fault zone in the oceanic ridge
system
Earthquakes
 Caused by friction from transform boundary plates
 Severity of an earthquake depends on
 The amount of stored potential energy
 The distance the rock mass moved when the energy was
released
 How far below the surface the movement occurred
 The makeup of the rock material
Volcanoes and tsunamis
Tsunamis
 A series of waves created when
a body of water is rapidly
displaced by an earthquake
 Can be generated when plate
boundaries abruptly move and
vertically displace the
overhead water
 Small wave heights offshore
and long wavelengths and
generally pass unnoticed out at
sea
 Mainly generated in the pacific
and Indian oceans
Volcanoes
 Active volcanoes produce
magma at the surface
 Other volcanoes are classified
as intermittent, dormant, or
extinct
 The majority occur at
subduction zones and midAtlantic ridges and the
remainder occur at hotspots
 The most common gases
formed by volcanoes are
steam, carbon dioxide, sulfur
dioxide, and hydrogen chloride
Seasons
 Seasons are affected by the amount of
solar energy on the earths surface, earths
rotation, earths revolution, and the tilt of
earths axis
 Summer occurs for the northern
hemisphere when it is pointed toward
the sun, which results in longer daylight
hours

Vise versa in the winter
 Actually in the winter the northern
hemisphere is closer to the sun
Review questions
1.
2.
3.
4.
5.
What are the three sections of the earth and what
do they include?
What accounts for the severity of an earthquake?
How is a tsunami created?
What are the main gases released by a volcanic
eruption?
What are all the factors of seasons?
Links
 Seasons: http://nitrogencycle.weebly.com/index.html
 plate tectonics, volcanoes, and earthquakes:
http://www.eoearth.org/article/AP_Environmental_Sci
ence_Chapter_3-_The_Solid_Earth
 Tsunamis: http://www.tsunami.noaa.gov/
Videos
 Plate tectonics:
http://www.youtube.com/watch?v=hqp_TbIZU64
 Volcanoes earthquakes, and tsunamis:
http://www.youtube.com/watch?v=XSUCRiKIql8