Ch 2 Earth’s Size & Shape
I. Model
A
representation of an object, a
process, or a phenomenon.
Ex.
– Globe – best, most to scale model
of the Earth
– Computer Climate
models/Simulations
II. A System

Part of the Universe that can be studied
separately
–
Closed System- a system in which
energy can enter or leave, but matter
cannot
–
Open System- a system in which
there is a free exchange of both
energy & matter between the system
& its surroundings.
III. Structure of the Earth
A. Inner Core - layer of the Earth
composed of solid iron & nickel
B. Outer Core - layer of the Earth
composed of liquid iron & nickel
Structure of the Earth Cont’
C. Mantle - largest Earth layer
 composed of silicon, oxygen,
magnesium, & iron
D. Crust - outer most layer of Earth
 the deepest mines & caves go no further
than the crust
 thicker under the continents than the
ocean
Layers of the Earth
IV.Temperatures Below the
Surface

Deep caves stay about the same
temperature all year

From 0 m to 20 m below, a cave usually
remains equal to the avg. yearly
temperature

Every 40 m below the 1st 20 m, the
temperature in a cave 10C for each 40
m (120ft)
Heat is from:

Radioactive Minerals
– Ex Uranium & Thorium

Compression of the crust by gravity
V. Earth’s Shape
A. Evidence that Earth is
Spherical
1. The mast of a ship is
the 1st part to appear
over the horizon &
the last to disappear.
Earth From Space
2.Photographs
of Earth from
space
Earth’s Shape Cont’
3. An eclipse of the moon occurs
when Earth's shadow falls on the
moon

The shadow is
always an arc of
a circle
http://www.rit.edu/~andpph/eclipse-01-20-00.htm l
Earth’s Shape Cont’
4. Ships sailing north or south observed
changes in the nighttime sky.

North Star appears higher in the sky as
a ship travels north

Ships sailing south lose sight of the Big
Dipper & begin to see the Southern
Cross
B. Oblate Spheroid

Sphere that is slightly flattened at the
poles & bulged at the equator

Caused by Earth's rotation
C. Weight on Earth
VI. Earth’s Density
A.
Density – The amount of matter
(mass) in a given space (volume)

Average density = 5.5 g/cm3
VII. Measuring Earth's Circumference
A. Eratosthenes (er uh Tos thuh neez)



Of Greek heritage, born in Cyrene,
now
Shah hat, (Libya)
Studied at Alexandria & Athens
Appointed Director of the Alexandrian
Library, 236 BC
Eratosthenes Cont’
Lived in Egypt
 1st Scientific Measurement of Earth’s
Circumference
 Went blind 195 BC
 Starved himself to death 194 BC

Facts Eratosthenes knew:

At noon on June 21st (Summer
solstice):
The sun casts a shadow of 7.2o
from an obelisk in Alexandria
The sun cast no shadow in a well
in Syene (called Aswan today)
Facts Eratosthenes knew:




Believed the suns rays hit the Earth as
parallel lines
Eratosthenes figured Syene was due south
of Alexandria (He was slightly off on this one)
Distance between Syene & Alexandria
(925km) slightly off
Thought both cities were on the same line of
longitude (off on this by 30)
VIII. Types of Data

Qualitative – data that is relative but not
numeric.
– Ex. The color of an object or stating
someone is tall or taller than another
person

Quantitative – data where a numeric
measurement or a count of objects has
been made
IX. 4 Spheres/Subdivisions of
Earth
1.
2.
3.
4.
Atmosphere
Geosphere
Hydrosphere
Biosphere
1. Atmosphere

Atmos- Greek, Meaning vapor
– Ozone- O3, protects Earth from Sun’s
harmful UV rays
– Oxygen & Carbon Dioxide provided for
living things
– Water vapor forms
clouds
2. Geosphere

Geo –Greek, meaning Earth
– Rocks, Mountains, Beaches
3. Hydrosphere

Hydro- Greek meaning water
– All the water of the Earth’s System
Oceans
Glaciers
Groundwater
Rivers
Lakes
4. Biosphere

Bio- Greek meaning Life
– All forms of life on Earth from microscopic
to Human