Download Chapter 2, Section 3 Internal Forces Shaping the Earth

Chapter 2, Section 3
Internal Forces Shaping the Earth
•Tectonic plates are moving pieces of the earth’s
lithosphere.
•Tectonic plates move in four ways:
•Spreading – moving apart
•Subduction – diving under another plate
•Collision – crashing into one another
•Sliding past each other in a shearing motion
Types of Plate Boundaries
• Divergent boundary – Plates move apart,
spreading horizontally; Saudi Arabia/Egypt –
causing the Red Sea to become wider.
• Convergent boundary – Plates collide, causing
one plate to dive under the other or the edges
of both plates to crumple; South Asia/India –
formation of the Himalayas.
• Transform boundary – Plates slide past each
other; North America/San Andreas fault in
California.
Earthquakes
• 95% of all earthquakes take place on
major plate boundaries. See picture on
page 37.
• Smaller-magnitude quakes that follow an
initial earthquake are called “aftershocks.”
–Aftershocks may occur for days after
the first quake.
Earthquakes
• Earthquakes are measured using the Richter
Scale (generally 0-10, but could be larger).
– The largest earthquake ever measured was 9.5 in
Southern Chile on May 22, 1960.
• Tsunamis are sometimes caused by
earthquakes that take place in the ocean.
– May travel up to 450 mph and produce waves 50100 feet high.
Volcanoes
• Magma, gases, and water from the lower part
of the crust or mantle collect in underground
chambers and eventually escape through a
crack in the earth’s surface (a volcano).
• Most volcanoes are found along tectonic plate
boundaries.
• Volcanoes do not erupt on a predictable
schedule – they may remain dormant (asleep)
for hundreds of years between eruptions.
Ring of Fire
• Zone around the Pacific Rim – location of the
vast majority of volcanoes.
• Eight major tectonic plates meet here.
• Other volcanoes appear over “hot spots”
where magma from deep in the mantle rises
and melts through the lithosphere (Hawaiian
Islands are an example of this).
More…
• Hot springs occur when ground water
circulates near a magma chamber.
• Geysers are hot springs that occasionally erupt
with steam jets and boiling water.
– Old Faithful erupts regularly, but most don’t.
• Volcanic ash produces fertile soil.
• Hot springs, steam, and heat generated from
magma can be used to create geothermal
energy (main source of energy in Iceland).