Transcript Chapter 4 Lesson 1 Plate Tectonics

Chapter 4
Lesson 1
Plate Tectonics
What Are Earth’s Layers
Earth’s Layers
• Core- central part
– Inner Core – solid
metals
– Outer Core – liquid
metals
• Mantle – thick layer of
solid and molten rock
that surrounds the
core
• Lower – solid rock
• Upper – 2 parts
• Lithosphere – solidupper mantle & crust
• Asthenosphere –
upper mantle – melted
rock
• Crust
– Thin layer of solid rock
that makes up the
outermost layer.
– Where we live
• Atmosphere –
– All gases that
surround the Earth
• Hydrosphere
– All of Earth’s liquid and
solid water (lakes,
oceans, rivers,
glaciers)
– Covers 70% of the
Earth
Landforms – a physical feature of
the Earth’s surface
Earth ~200 million years ago
The Continental Drift Hypothesis
Geologist – person that studies rocks
Thought of by Alfred Wegener in 1915.
Continents "drifted" to their present positions.
Supercontinent Pangaea started to break up
about 200 million years ago.
Continental Drift: Evidence
Geographic fit of South America and Africa
Fossils match across oceans
Rock types and structures match across
oceans
Ancient glacial features
Continental
Drift:
Evidence
Tight fit of
the
continents,
especially
using
continental
shelves.
Continental Drift:
Evidence
Fossil critters and plants
Continental
Drift:
Evidence
Correlation of
mountains
with nearly
identical rocks
and structures
Continental
Drift:
Evidence
Glacial
features
of the same
age
restore to a
tight polar
distribution.
Presumably,
Pangaea was
ripped apart by
such continental
rifting & drifting.
What causes the
continents to move?
Plate Tectonics
•Theory to explain how
forces deep within Earth
can cause seafloors to
spread and continents to
move.
Tectonic Plates
Continental Divergent Boundary
Example: Red Sea / E. African Rift
• Magma – hot melted rock
• Tension – push or a stretch on the plates
• Seafloor Spreading – caused by magma
pushing on the plates
Mid Ocean Ridges
-
underwater
mountain
ranges
Subduction – when one tectonic
plate can sink under another platecrust gets recycled back into the
mantle
•
Mountain
Formation
Compression – a squeezing
or pushing together of the
crust
This creates folded mountains.
Fault – deep cracks in the Earth’s crust
where rocks move in the opposite direction
• Fault Block
Mountain
– Caused by tension
when one block of
rock moves down
– Sierra Nevada
Mountains