Download 無投影片標題

海洋科學：地質面向
Birth of an island
The Earth in cross section
The chemical and
physical
organization of the
Earth’s Layers
compared
The layering of
the lithosphere
and
asthenosphere
in more detail
Characteristics of the Earth’s Layers
大陸飄移假說
（Continental Drifting Hypothesis）→
海底擴展學說（Seafloor Spreading）→
板塊構造學說（Plate Techtonics）
Seismic events worldwide,
January 1977 through December 1986
The fit of all the
continents around
the Atlantic
Reconstruction of Pangaea
The major lithosphere plates
板塊構造學說
（Plate Techtonics）
An overview of the plate tectonics process
The formation of
a new plate
boundary:
the breakup of
Pangaea
The South Atlantic in cross section, showing the
mid-ocean ridge at a divergent plate boundary
A cross section through
the west coast of South
America
The formation of an island arc along a
trench as two oceanic plates converge
The convergence of two continental plates
Characteristics of the Plate Boundaries
A long transform
plate boundary
Key Concepts for Plate Tectonics (I)
• Earth is composed of concentric spherical layers, with the least
dense layer on the outside and the densest as the core.
• The lithosphere, the outmost solid shell that includes the crust,
floats on the hot, deformable asthenosphere. The mantle is the
largest of the layers.
• Large regions of Earth’s continents are held above sea level by
isostatic equilibrium, a process analogous to a ship floating
in water.
• Some seismic waves – energy associated with earthquakes – can
pass through the Earth. Analysis of how these waves are changed,
and the time required for their passage, has told researchers much
about conditions inside Earth.
Key Concepts for Plate Tectonics (II)
• Plate tectonics theory suggests that Earth’s surface is
not a static arrangement of continents and ocean, but a
dynamic mosaic of jostling segments of lithosphere
called lithospheric plates. The plates have collided,
moved apart, and slipped past one another since
Earth’s crust first solidified.
•
Plate motion is driven by slow, heat-generated
(convection) currents flowing in the mantle. Most of the
heat is generated by the decay of radioactive elements
within Earth.
Key Concepts for Plate Tectonics (III)
• Most of the large-scale features seen at Earth surface
may be explained by the interactions of plate tectonics.
Plate tectonics also explains why our ancient planet has
surprisingly young seafloors, the oldest of which is only
as old as the dinosaurs, that is, about 1/23 the age of
Earth.
•
The confirmation of plate tectonics rests on diverse
scientific studies from many disciplines. Among the
most convincing is the study paleomagnetism, the
orientation of Earth’s magnetic field frozen into rocks
as it solidified.
The End
Thank you for your attention
(if you have been staying awake)