Transcript Notes 11 – Earth`s Interior

Notes 11 – Plate
Tectonics
Earth Science
Mrs. Gordon
Friday, April 8, 2016
Review of Earth’s Layers:
• Crust
– Oceanic Crust – ocean
floor, made of dense basalt,
thinner part of crust
– Continental Crust – less
dense, mostly granite, thicker
• Asthenosphere – soft material
that can flow like warm plastic
• Mantle
• Core
– Outer core – liquid rock
– Inner core – solid, very dense
metal
• NOTE: the inner and
outer core rotate and
create Earth’s magnetic
field
Seafloor spreading review
~ Wegener's evidence + discovery
of sea floor spreading led to:
• A. The Theory of Plate Tectonics pieces of Earth’s crust are in constant,
slow motion driven by convection
currents in the mantle.
• Every plate affects the other plates around
it by colliding together, ripping apart or
grinding past each other.
• 1. The driving force of Plate Tectonics are CONVECTION
CURRENTS. (Heat RADIATES out from the core,
warms mantle, material rises, then cools and sinks)
Convection means ‘heat
transfer’. When a fluid heats up,
the density decreases and it
rises, eventually cooling,
condensing and sinking again.
B. Where does Earths’ internal
heat come from?
• 1. Radioactive Decay - elements break down into other
elements and release heat energy
• 2. Residual heat - left over from our planets formation
C. What will happen when Earth’s
internal heat runs out?
•
•
•
•
No plate movement
No volcanoes
No earthquakes
No mountain building
• D. Plate
Boundaries –
edges of
Earth’s crustal
plates that
extend deep
into the
lithosphere
Write these definitions, along
with ARROWS showing
directions of movement, on
the left side page across from
these notes – divide page into
4 sections.
• 1. Convergent
Boundaries - Where two
plates smash together
(results in the process of either
subduction (trenches and
volcanoes) or mountain building
(mountains)
– C-C
– O-C
– O-O
• Subduction zones – deep
trenches where one plate
slides under another.
• The plate will melt as it is
pushed deep underground.
• 2. Divergent Boundaries – Where plates
are ripping away from each other.
• O-O = Results are mid-ocean ridges (new
ocean floor is formed here)
• C-C = Results are rift-valleys
• 3. Transform Boundaries – Where plates
slide (grind) past each other in opposite
directions. (San Andreas Fault)
THE BIG PICTURE
Old / Extra stuff:
How do we know what's inside
Earth?
• Geologists use many different forms of
indirect evidence to hypothesize what
Earth’s interior is composed of.
• Ex: Earthquakes, seismic waves, plate
movement, drilling
• Its tough to see first hand b/c as you go
deeper underground both temperature and
pressure increase.
• Cool link: Deep Drilling
• 1. Theory of Continental Drift – all
continents were once connected and
called Pangaea, they have since drifted
apart.
• A. Alfred Wegener
German scientist,1910
B. Evidence:
• Landforms, rock layers and
fossils match up across the oceans
• Seafloor spreading
• Observing
forces
happening
today
A. Sea Floor Spreading
1. PROCESS =
~ Magma is forced upwards towards the crust,
between two plates.
~ Magma fills the gap that is created.
~ Magma hardens to form new ocean crust.
2. EVIDENCE = molten material,
hydrothermal vents, magnetic
stripes, drilling samples