THE SEA FLOOR: LAYERS OF
THE EARTH
Ms. Springstroh
Why study the sea floor in
this class?
 Over time, geological processes greatly
influence marine habitats.
 Sculpt the shoreline
 Determine water depth
 Control the substrate on the ocean floor (rock,
sand, mud, etc)
 Create new underwater mountains for organisms
to live on
Oceans
 Cover 71% of the earth’s surface
 Regulate earth’s climate and atmosphere
Fun facts about the oceans
 Northern Hemisphere = 61% ocean
 Southern Hemisphere = 80% ocean
 Pacific ocean: deepest, largest, almost as
large as all the others combined
 Arctic ocean is the smallest and shallowest
 Because all of the oceans are connected, they
are sometimes referred to as a single “world
ocean”.
Formation of the earth
 Big Bang
 13.7 billion years ago
 Cosmic explosion which produced dust
 Dust particles from the big bang collided with
each other
 Created larger particles
 More collisions lead to even larger particles
 These collisions created the earth (4.5 billion years
ago) and other planets
When the earth was created…
 It was probably molten (liquified by heat)
 This allowed the materials within the earth to
settle according to density.
Density
 Density =
object’s mass__
object’s volume
 Remember: mass is similar to weight
volume is how much space an object
takes up
 Which do you think is more dense? A pound
of styrofoam or a pound of lead?
lead
Density (continued)
 Less dense materials float, or rise on top of,
more dense materials
Which object in this
picture is more
dense?
The water
Density (continued)
 When the earth was molten, where would
you find the most dense material?
 In the center of the planet
 Where would you
find the lightest
material?
 Toward the surface
of the planet
Layers of the earth
 Extremely high pressure and temperatures
formed the core




Innermost layer of the earth
Composed mostly of iron
Estimated to be 7,200°F
Made of two parts:
 Inner core (solid)
 Outer core (liquid)
 Swirling motions of iron-containing material in the
outer core might be what produces earth’s magnetic
field
Layers of the earth
(continued)
 Outside of the core is the earth’s mantle
 Solid, but very hot, so it can flow like a liquid
 Contains the upper mantle and the lower mantle
 Outside of the mantle is the earth’s crust
 Outer-most layer of the earth
 Very thin
 Contains the oceans and the continents
Earth’s crust
 There are two types of crust:
 Oceanic crust
 Made of a mineral called basalt
 Covered with water (the oceans)
 Continental crust
 Made of granite
 Oceanic crust is more dense than continental
crust. This makes sense, because oceanic crust is
“below sea level” and covered with water, and the
continents lie high and dry above sea level.
Asthenosphere and
Lithosphere
 The asthenosphere is closer to the earth’s
core and contains part of the upper mantle
 The lithosphere is closer to the surface of the
earth and contains the rest of the upper
mantle and all of the crust
On your drawing, label and
color the following:






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Inner core
Outer core
Lower Mantle
Upper Mantle
Continental Crust
Oceanic Crust
Asthenosphere
Lithosphere