CH. 10.2 Intrusive Igneous Activity
“What’s a pluton?”
Structures that result
from the cooling low
and hardening of
magma below the
earth’s surface.
Classified by their
shape, size, and
relationship to
surrounding rocks.
Sill = forms when magma is injected along
sedimentary rock layers parallel to the layers.
Laccolith = forms when magma is injected along
sedimentary rock layers parallel to the layers
creating a lens-shaped mass that pushes the
overlying layer upwards.
Dikes = when magma is injected into fractures
cutting across pre-existing rock layers.
Batholiths = an igneous intrusion that is over 100
km2 in size.
Origin of Magma
Solid rock located in the crust and upper mantle melts.
How does the rock get heated enough to melt?
Geothermal Gradient
Temperature gets hotter
as you go deeper.
About 20o C to 30o C per
kilometer.
This gets the rocks to
ALMOST melting……….
…… Friction from
subduction zones heats
the rock the rest of the
way.
OR
…… Crustal rocks heat up
as they descend into the
mantle.
OR
…… Hotter mantle rock
rise and intrude crustal
rock.
These processes only make small amounts of magma.
Pressure Melting
Rocks Can! It’s when the pressure is
released that they melt.
Remember…
Rocks deep in the
Earth are solid
because of the
immense pressure.
Wet Melting
Pressure and Wet Melting:
http://www.fccj.info/gly1001/animations/Chapter9/MagmaMelting.html
Plate Tectonics and Igneous Activity
In the Zone… Three Zones of Volcanism:
• Convergent Plate Boundaries
• Ocean-Ocean
• Ocean-Continent
• Divergent Plate Boundaries
• Intraplate Igneous Activity
• Hot Spots at Mantle Plumes
HOW THE EARTH WORKS pg 298-299
Read pgs 298-299.
Answer the Assessment Quesitons on pg 299.