Download Geologic Time and Plate Tectonics

Geologic Time and Plate Tectonics
CH. 1 in Barron’s
Textbook CH. 8 (New Book)
GEOLOGIC TIMESCALE


Geologists have divided Earth's history into a series of time intervals.
The geologic time scale was constructed to visually show the duration of each time
unit.

The Earth is 4.6 billion years old.
• The geologic processes have
been happening for a very
long time.
• Humans just showed up at
the end.
The Earth Is a Dynamic Planet
• The earth’s interior consists of:
– Core: innermost zone with solid inner core and molten outer
core that is extremely hot
– Mantle: liquid rock with a rigid outer part (asthenosphere) that
is melted pliable rock
– Crust: layer of solid rock (lithosphere) which underlies the
continents and the oceans
• Continental crust
• Oceanic crust
Major Features of the Earth’s Crust
and Upper Mantle

Major features of the earth’s crust and upper mantle.
The Earth Beneath Your Feet is Moving
• Plate Tectonics
– The theory that Earth’s crust is divided into huge
tectonic plates that float on magma or molten rock.
– Convection currents within the mantle move the
plates around.
– Evidence:
• Puzzle-like fit of the continents
• Matching plant/animal fossils on
sides of oceans
• Matching rock layers on opposite
oceans
• Evidence of past climates
opposite
sides of
The Earth’s Major Tectonic Plates
Spreading
center
Collision between two
continents
Ocean
trench
Oceanic
crust
Oceanic
Subduction zone
crust
Continental
crust
Continental crust
Material cools Cold
as dense material
it reaches the falls back through
outer mantle
mantle
Mantle
convection
cell
Two plates move towards
each other. One is
subducted back into the
mantle on a falling
convection current.
Hot
material
rising
through
the mantle
Mantle
Hot outer
core Inner
core
Fig. 15-3, p. 337
Tectonic Plate Boundaries
• Plates move apart at
divergent plate
boundaries.


Mid-ocean ridge – the site of sea-floor spreading
Great Rifts – if on land
Tectonic Plate Boundaries
 Plates grind into one
another at convergent
plate boundaries.



2 continental crusts colliding lifts a mountain
chain
Oceanic and continental collide – oceanic
subducts underneath the continental.
Volcanoes on continent side, trench on
ocean side
2 oceanic crusts collide: one subducts under
the other and you get a trench and a volcanic
island arc
Tectonic Plate Boundaries
 Plates slide past one another at transform plate
boundaries.
Volcanoes Release Molten Rock
from the Earth’s Interior
 Volcanoes are simply vents in the
earth's surface through which lava and
other volcanic products erupt.