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Welcome Chapter to the neighborhood
Magnetic field- the region affected by the force emanating from a magnet.
Earth's magnetic field is largely a dipole meaning it has a north and south pole
Magnetic field deflects most of solar wind so that most of the particles in the wind
do not reach Earth's surface
Particularly strong bursts of solar wind can disrupt the electronics on spacecraft
Van Allen radiation belts consist of solar wind particles as well as cosmic rays that
move so fast they are able to penetrate the weaker outer part of the magnetic field
and are trapped by the stronger magnetic field closer to the earth. The Van Allen
radiation belt protects life on Earth from dangerous radiation.
Particles that make it past the Van Allen belts interact with gases in the upper
atmosphere and glow, creating aurorae
The Atmosphere
atmosphere- an envelope of gas consisting of 78% nitrogen and 21% oxygen with 1% of
other gases
Weight of overlying air squeezes on the air below and pushes gas molecules in the
air below closer together, thus both the density of air and air pressure decrease
with increasing elevation
Land and Oceans
Earth is 30% dry land 70% water
hydrospheres- surface water on earth along with groundwater
cryosphere-ice-covered regions
topography- physical features of the land surface represented by changes in
elevation
hypsometric curve- a graph plotting surface elevation on the vertical axis and the
percentage of the earth's surface on the horizontal axis and the percentage of the
Earth's surface on the horizontal axis
What is the Earth made of?
iron 35%, oxygen 30%, silicon 15%, magnesium 10% make up most of the earth's
mass remaining 10% consists of the other 84 naturally occurring elements
Categories of Earth Materials
o Organic chemicals ie. carbon, co2, oil, protein, rubber, plastic, fat
o Minerals - a solid substance in which atoms are arranged in an orderly
pattern.
o Glasses- a solid in which atoms are not arranged in an orderly pattern.
Forms when a liquid freezes so fast that atoms do not have time to
organize into an orderly pattern
o Rocks- aggregates of mineral crystals or grains, and masses of natural gas
Igneous rocks- form from hot molten rocks cooled and frozen solid
Sedimentary rocks- form from grains that break off preexisting
rock and become cemented together
Metamorphic rocks- created when preexisting rocks undergo
changes such as the growth of new minerals in response to heat
and pressure
o Metals- solids composed of metal atoms such as iron, aluminum, copper,
and tin. an alloy is a mixture containing more than one type of metal atom
o Melts- formed when solid materials become hot and transform into liquid
eg. molten rock
o Volatiles- materials that easily transform into gas at the relatively low
temperatures found at the earth's surface
Most common minerals in the earth contain silica
Four classes of igneous silicate rocks based on proportion the of silicon to iron
and magnesium. Felsic, intermediate, mafic, and ultramafic.
4 Rock names: granite, basalt, gabbro, peridotite
How do we know that the earth has layers?
Earth resembles a hardboiled egg in that it has three principal layers.
o crust- a not so dense crust composed of rocks like granite, basalt
o mantle- denser solid layer composed of then-unknown material
o core- very dense material
Earthquake- ground shaking due to the sudden breaking of rocks in the Earth
Fault- a fracture on which sliding occurs
Pressure and temperature increasing with depth in the earth.
Geothermal gradient- rate of change in temperature with depth
What are the layers made of?
The Crust
o Depth of about 50km. Only 0.1 to 1% of the Earth's radius
o Two types of crust, oceanic and continental crust. Crust consists of a
variety of rocks that differ in composition from mantle rock
o Oceanic crust only 7 to 10 km thick. Has fairly uniform layers. At the top
we find a blanket of sediment composed of clay and tiny shells, beneath
the blanket is the oceanic crust consisting of a layer of basalt and below
that, a layer of gabbro
o Continental crust is about 35 to 50 km thick. Continental crust contains a
great variety of rock types, ranging from mafic to felsic
o On average continental crust is less mafic than oceanic crust, average
continental crust weighs less than oceanic crust
o Oxygen is by far the most abundant element in the crust (93% of the crust)
The Mantle
o Mantle is the largest part of the Earth
o The mantle consists entirely of an ultramafic rock called peridotite
o Mantle divided into two sublayers
Upper mantle- down to the depth of 660 km
lower mantle- 660 km down to 2900 km
o The interval lying between 400 km and 660 km keep is called the
transition zone because here the character of the mantle undergoes a series
of abrupt changes
o Most of mantle is solid rock
o A few percent of the mantle has melted in a layer that lies at depths of
between 100 and 200 km beneath the ocean floor. Melt causes seismic
waves to slow down
The Core
o The outer core is a liquid iron alloy from 2900 to 5155 km deep. I can
exist as a liquid because the temperature in the outer core is so high that
even the great pressures squeezing he region cannot lock atoms into a
solid framework. The iron alloy of the outer core can flow and thus
generates the Earth's magnetic field
o The inner core from 5155 to the earth's center at 6371 km is a solid ironnickel alloy. Though hotter than the outer core, the inner core is solid
because it is deeper and subjected to even greater pressure, the atoms are
kept from wandering freely so they pack together tightly.
The Lithosphere and Asthenosphere
The lithosphere is composed of the layers that have rock that cannot flow easily,
consists of the curst plus the uppermost part of the mantle
Asthenosphere is the portion of the mantle in which rock can flow