2.2a The interior of Earth is hot. Heat flow and movement of material within Earth

cause sections of Earth’s crust to move. This may result in earthquakes, volcanic

eruption, and the creation of mountains and ocean basins.

2.2b Analysis of earthquake wave data (vibrational disturbances) leads to the conclusion that there are layers within Earth. These layers of the crust, mantle, outer core, and

inner core have distinct properties.

2.2c Folded, tilted, faulted, and displaced rock layers suggest past crustal movement.

2.2d Continents fitting together like puzzle parts and fossil correlations provided initial

evidence that continents were once together.

2.2e The Theory of Plate Tectonics explains how the solid lithosphere consists of a

series of plates that float on the partially molten section of the mantle. Convection

cells within the mantle may be the driving force for the movement of the plates.

2.2f Plates may collide, move apart, or slide past one another. Most volcanic activity

and mountain building occur at the boundaries of these plates, often resulting in earth-


2.2g Rocks are classified according to their method of formation. The three classes of

rocks are sedimentary, metamorphic, and igneous. Most rocks show characteristics that

give clues to their formation conditions.

2.2h The rock cycle model shows how types of rock or rock material may be transformed from one type of rock to another.

2.2i Weather describes the conditions of the atmosphere at a given location for a short

period of time.

2.2j Climate is the characteristic weather that prevails from season to season and year

to year.

2.2k The uneven heating of Earth’s surface is the cause of weather.

2.2l Air masses form when air remains nearly stationary over a large section of Earth’s

surface and takes on the conditions of temperature and humidity from that location.

Weather conditions at a location are determined primarily by temperature, humidity,

and pressure of air masses over that location.

2.2m Most local weather condition changes are caused by movement of air masses.

2.2n The movement of air masses is determined by prevailing winds and upper air currents.

2.2o Fronts are boundaries between air masses. Precipitation is likely to occur at these


2.2p High-pressure systems generally bring fair weather. Low-pressure systems usually

bring cloudy, unstable conditions. The general movement of highs and lows is from

west to east across the United States.

2.2q Hazardous weather conditions include thunderstorms, tornadoes, hurricanes, ice

storms, and blizzards. Humans can prepare for and respond to these conditions if given

sufficient warning.

2.2r Substances enter the atmosphere naturally and from human activity. Some of these

substances include dust from volcanic eruptions and greenhouse gases such as carbon

dioxide, methane, and water vapor. These substances can affect weather, climate, and

living things.