CHAPTER 2
Section 1 – Earth: A Unique Planet
Earth Basics
Third planet from the sun in our solar system
4.6 billions years old
71% of the surface is covered by water
Global ocean – relatively thin layer of water that covers earth’s surface
shape of earth is an oblate spheroid – slightly flattened sphere
polar regions flatten and the equator is bulged (why?)
surface is relatively smooth
Earth’s Interior
Discoveries made by seismic waves – vibrations that travel through earth
Compositional Zones
1. crust – thin, solid outermost zone of Earth
a.
oceanic crust – crust beneath oceans
b. continental crust – crust that makes up the continents
2. mantle – the layer that underlies the crust
a.
denser than the crust
b. nearly 2900 km thick
c.
2/3 of earth’s mass
3. core – central part of the Earth below the mantle
a.
iron
b. nickel
Structural Zones
1. lithosphere – the solid, outer layer of Earth that consist of the crust and the rigid upper part of the mantle
2. asthenosphere – the solid, plastic layer of the mantle beneath the lithosphere; made of mantle rock that flows very slowly, which allows
tectonic plates to move on top of it
3. mesosphere – the “middle sphere”; the strong lower part of the mantle between the asthenosphere and the outer core
4. outer core – a dense liquid at a depth of 2900 km
5. inner core – a dense, rigid solid at a depth of 5900 km
Earth as a Magnet
Two magnetic poles
Extends beyond the atmosphere and affects a region of space called
the magnetosphere
- source may be the liquid iron core
- may be produced by motions within the core that produces electric currents that in turn create Earth’s magnetic field
- Sun and Moon also have magnetic fields
Earth’s Gravity
Gravity – the force of attraction that exists between all matter in the universe
Law of Gravitation – the force of attraction between any two objects depends on the masses of the objects and distance between
the two objects
Weight and Mass
Weight – a measure of the strength of the pull of gravity on an object. The Newton (N) is the SI unit used to measure
weight.
The mass of an object does not change regardless of location, but the weight of the object will change. Why?
Weight and Location
Weight varies according to the location on Earth’s surface.
Weight at the equator would be about 0.3% less than the weight at the poles. Why?
Section 2 Energy in the Earth System
System
an organized group of related objects or components that interact to create a whole
vary in size (subatomic to universe)
all have boundaries
Earth system is an interaction between matter and energy
o
Matter – anything that has mass and volume
o
Energy – the ability to do work

Heat

Light

Vibrations

Electromagnetic waves
Closed system – energy is exchanged, not matter
Open system – both energy and matter are exchanged
Earth system is almost closed because matter exchange is very limited
Earth’s Four Spheres
Atmosphere
blanket of gases that surrounds Earth’s surface
provides the air that you breath
shields Earth from sun’s harmful radiation
78% nitrogen, 21% oxygen and 1% a mixture of gases
Hydrosphere
all of Earth’s water except the water that is in gaseous form in the atmosphere
71% of Earth’s surface is covered
97% of water is in salty oceans
Geosphere
mostly solid part of the Earth
all of the rock and soil on the surface and on the ocean floor
includes the solid and molten interior of the Earth
Biosphere
composed of all of the forms of life in the geosphere, in the hydrosphere, and in the atmosphere
any organic matter that has not decomposed
extends from the deepest parts of the ocean to the atmosphere a few kilometers above Earth’s surface
Earth’s Energy Budget
First law of Thermodynamics
Energy Budget
Second law of Thermodynamics
Internal Energy Sources
decay of radioactive atoms
convection – movement of hot materials toward the surface
o
cooler, denser materials sink
o
this process drives plate tectonics
External Energy Sources
sun
o
movement of air masses
o
generates wind and ocean currents
o
allows plants to produce food
the pull of the sun and the moon on the oceans, combined with Earth’s rotation, generates tides that cause currents and drive the mixing of ocean water
Cycles in the Earth System
Reservoir – a place where matter and energy is stored
Cycle – a group of processes in which matter and energy repeatedly move through a series of reservoirs
Nitrogen Cycle – nitrogen moves from air to soil, soil to plants and animals and back to air again
Carbon Cycle
Phosphorous Cycle – moves through every sphere except the atmosphere
Water Cycle – water to gas to precipitation to water
Section 3 – Ecology
Ecology – the study of the complex relationships between living things and their non-living, or abiotic, environment
Ecosystems
A community of organisms and their abiotic environment
Producers – organisms that can make their own food
Consumers – organisms that get their energy by eating other organisms
Decomposers – organisms that get their energy by breaking down dead organisms
Balancing Forces in Ecosystems
Carrying capacity – the largest population that an environment can support at any given time
Ecological Responses to Change
ecosystems react to changes in ways to maintain or restore balance in the ecosystem
predictable patterns of return to a damaged ecosystem
o
grasses and fast growing plants start to grow
o
shrubs and small animal species will return
o
larger tree species and larger animals return
Energy Transfer
ultimate source or energy is the sun
photosynthesis – plants using sunlight to produce food
energy pyramid
o
producers form the base
o
consumers form the next level
o
decomposers form the top of the pyramid

as you move up the pyramid, more energy is lost at each level
Food Chains and Food Webs
food chain – the sequence in which organisms consume other organisms
food web – a diagram that shows the feeding relationships among organisms in an ecosystem
Human Stewardship of the Environment
Ecological balances can be disrupted by human activity
o
Overconsumption of resources
o
Conversion of natural areas to agriculture or urban areas
o
Pollution – the contamination of the environment with harmful waste products or impurities