Notes
2: Structure of Earth
1. Explain three pieces of evidence about Earth’s spherical shape that was
known even thousands of years ago.
1.
The mast of a ship was the first to appear over the horizon.
2.
The lunar eclipse is circular
3. When ships traveled North or south the night sky changed
2.
Explain how gravity shows that the earth is: (a) round.
The
forces of gravity are the same around the earth
(b)
An Oblate spheroid.
195 kilograms at the poles =194 kilograms at the equator.
The
poles are closer to the center than the equator by 68 kilometers. Why?
The
Earth’s spinning?
3.
Explain how Eratosthenes measured earth’s circumference.
He
knew that at the summer solstice the sun shone directly into a well at Syene at
noon. At the same time, in
Alexandria
,
Egypt
, approximately 787 km due north of Syene (now
Aswan
), the angle of inclination of the
sun’s rays was about 7.2°
With these measurements he computed the diameter and circumference of the earth.
He determined Earth's circumference to be ~40,000 km.
Density
of the Earth Increases
as you travel from the crust to the core
The
two structures that make up the lithosphere are:
the crust and the upper mantle
The
layer within the mantle that the lithosphere rests on is the:
Asthenosphere
•
Part
of mantle
•
Hot,
weak rock
•
Plastic
flow in convection cells
•
Moves
overlying plates
The
largest part of the earth is the core, which is believed to be made chiefly of:
Iron and nickel
Outer
core
•
Liquid
•
Metallic
•
Causes
magnetic field
Inner
core
•
Solid
•
Metallic
The
inner core has a diameter of about 2600 kilometers
The inner and outer core are divided because they have different: states.
Solid inner/ liquid outer
The
crust is approximately 5 to 40 kilometers thick
Test
borings indicate that the temperature of the earth's interior:
increases with depth by 1°C for
every 20 meters
HEAT
OF EARTH
•
from
“original” heat
•
radioactive
heat
•
convection
of heat from core
Geothermal
Gradient
The
Earth is about 4.5 billion tears old.
The
average temperature on earth is 14 degrees Celsius
The
land surface of earth comprises about 150 million square kilometers
70%
of the earth’s surface is covered by water.
The
oldest rock on earth is less than 3 billion years old because of the
“recycling” rock cycle
The
solid rock seen at the surface is called outcrops.
This rock that appears to go down forever is called the bedrock
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