Class Notes for 9/8-9/16
The Earth Within the Universe
I. The Solar System
- our solar system is in the Milky Way galaxy
- the solar system is 6 billion years old
A. The Sun
- the Sun is the star at the center (solar = sun)
- the Sun is the
largest body in the solar system
- has a
diameter of 870,000 miles (1,390,000
km)
B. The Planets
- there are 10 planets in our solar system as of
January 5, 2005
- the first four are classified as the terrestrial planets
(Mercury, Venus, Earth, and Mars)
- the next four are classified as the gaseous giants (Jupiter, Saturn, Uranus, and Neptune)
- Pluto is a tiny planet with an
irregular orbit
- the new tenth planet is temporarily called 2003 UB313
and is very similar to PlutoC. Other Bodies in the Solar System
- comets are dirty snowballs that
travel in orbits around the sun
- asteroids are large boulder-
to mountain-sized rocks that are found mainly in a belt between Mars and Jupiter
- meteoroids are rocks that are
smaller than asteroids
- called a meteor if it enters Earth's atmosphere
and is seen as a streak of light
- if the meteor does not burn up in the atmosphere and crashes into the Earth, it is called a meteorite
II. Planet Earth
- Earth is unique because of its water, oxygen, and nitrogen
A. The Moon
- Earth's only natural satellite is the Moon
- the Moon reflects some of the Sun's light and appears to shine
- amount of light reflected varies, so we see the Moon in phases
- full moon, new gibbous (
waning),
first quarter, new crescent, new moon, old crescent, last quarter, old gibbous (waxing)
- revolves around the Earth and rotates on its own axis
- always shows the same side to the Earth because the rates of revolution and rotation are the same
- takes
27.3 days to make one complete revolution
around Earth
- the Moon affects the ocean's tides
- there are
2 high tides and 2 low tides every 24 hours
- the full moon causes very high tides
B. Time on Earth
- the Earth spins (rotates) on its axis and revolves around the Sun
- one complete turn on the axis is one
day (24 hours)
- one complete turn around the Sun is one
year (365.4 days)
C. Seasons
- seasons occur because the Earth is tilted 23.5 degrees on its axis
- this tilt allows some areas of the planet to get more sunlight than others
- the equator divides the Earth into the Northern Hemisphere and Southern Hemisphere
- the hemisphere must be tilted towards the sun in order for summer to occur as a result of direct rays
- New York is in the Northern Hemisphere
-first day of winter is on December 21 (
winter solstice)
- shortest day of the year with the direct sunlight on the Tropic of Capricorn
- first day of summer is on June 21 (
summer solstice)
- longest day of the year with direct sunlight on the Tropic of Cancer
- first day of spring is on March 21 (
vernal equinox), and the first day of autumn is on September 23 (autumnal
equinox)
- both days have 12 hours of sunlight with the direct rays on the equator
The Anatomy of Earth
I. Overview of Earth’s Composition
- the
lithosphere is the outer layer
of the Earth (the crust)
- the crust is made up of rock, soil, and some common elements (O2, Si, Al, Fe, Ca, Na, K, Mg)
- 71% of the crust is covered with water
- all areas of water make up the
hydrosphere
- the
atmosphere is made up of gases
that sit on the crust (78% N2, 21% O2, 1% Ar, CO2, H2O)
- the
core of the Earth is molten and
made out of Fe and Ni
- the core is denser than the lithosphere
II. The Crust
- made of minerals like gold, copper, carbon, feldspar, mica, quartz, and calcite
- minerals can form
crystals if they
are changed by heat and pressure
-
igneous rocks are made when magma
cools
- magma can also flow out of the crust as lava
-
sedimentary rocks are made of particles
that become cemented together
-
metamorphic rocks are made when existing
rocks are changed by heat and pressure
A. The Continents
- at the present, there are seven continents (Africa, Asia, Europe, Australia, Antarctica, North America, South America)
- in 1912, Alfred Wegener proposed that
there was once one giant continental landmass called Pangaea
- Pangaea means all Earth
- continental drift caused Pangaea to
break up into pieces and move on the crust
- Gondwanaland was in the south, and
Eurasia was in the North
- theory was proven to be correct because of the puzzle-like fit of Africa and South America, the similarities of rock
formations, and similarities of fossils in both continents
- Wegener’s theory was not accepted until the 1960s
- ridges and cracks were found in the sea floor
- magma flowed out of the Earth and widened the sea floor, pushing the continents apart
B. Crust Under the Sea
- the mid-ocean ridge is the largest
mountain chain on Earth
- there are rift valleys
- the sea floor surfaces to form volcanoes
- there are faults (cracks) in the sea floor where movement occurs
- the farther away from the mid-ocean ridge a rock is, the older it is
- new magma flows out of the faults and pushes the old rocks away
- old rocks are pushed into deep trenches in the crust and may melt (subduction)
- the deepest trench in the world is the Mariana Trench
- a series of trenches in the Pacific Ocean
make up the Ring of Fire, an area of immense
volcanic activity
C. Plate Tectonics
- the continents and the sea floor rest on plates
- plates are large pieces of crust that float on the mantle
- there are 12 very large plates and several smaller ones
- the continental plates are lighter than the sea floor plates
- the plates move constantly
- volcanoes form when the sea floor plates push under the continental plates
- mountains form when continental plates collide
- areas known as
transform boundaries where
there is a lot of plate movement are earthquake sites
- the plates grind together, as on the San Andreas fault line
D. The Future of the Earth’s Crust
- the Atlantic Ocean will become wider, whereas the Pacific Ocean will become narrower
- Africa will move north
- the Mediterranean Sea will dry up
- a new mountain range will stretch from Africa to Turkey when African crashes into Asia
- Australia will move north
- California will separate from North America and become a series of islands
