2.1a Earth systems have internal and external sources of energy, both of which create


2.1b The transfer of heat energy within the atmosphere, the hydrosphere, and EarthÕs

interior results in the formation of regions of different densities. These density

differences result in motion.

2.1c Weather patterns become evident when weather variables are observed, measured,

and recorded. These variables include air temperature, air pressure, moisture (relative

humidity and dewpoint), precipitation (rain, snow, hail, sleet, etc.), wind speed and

direction, and cloud cover.

2.1d Weather variables are measured using instruments such as thermometers,

barometers, psychrometers, precipitation gauges, anemometers, and wind vanes.

2.1e Weather variables are interrelated.

For example:

¥ temperature and humidity affect air pressure and probability of precipitation

¥ air pressure gradient controls wind velocity

2.1f Air temperature, dewpoint, cloud formation, and precipitation are affected by the

expansion and contraction of air due to vertical atmospheric movement.

2.1g Weather variables can be represented in a variety of formats including radar and

satellite images, weather maps (including station models, isobars, and fronts), atmos-

pheric cross-sections, and computer models.

2.1h Atmospheric moisture, temperature and pressure distributions; jet streams, wind;

air masses and frontal boundaries; and the movement of cyclonic systems and associ-

ated tornadoes, thunderstorms, and hurricanes occur in observable patterns. Loss of

property, personal injury, and loss of life can be reduced by effective emergency


2.1i Seasonal changes can be explained using concepts of density and heat energy.

These changes include the shifting of global temperature zones, the shifting of planetary

wind and ocean current patterns, the occurrence of monsoons, hurricanes, flooding, and

severe weather.

2.1j Properties of Earth’s internal structure (crust, mantle, inner core, and outer core)

can be inferred from the analysis of the behavior of seismic waves (including velocity

and refraction).

¥ Analysis of seismic waves allows the determination of the location of earthquake epicen-

ters, and the measurement of earthquake magnitude; this analysis leads to the inference

that Earth’s interior is composed of layers that differ in composition and states of matter.

2.1k The outward transfer of Earth’s internal heat drives convective circulation in the

mantle that moves the lithospheric plates comprising Earth’s surface.

2.1l The lithosphere consists of separate plates that ride on the more fluid asthenosphere

and move slowly in relationship to one another, creating convergent, divergent, and trans-

form plate boundaries. These motions indicate Earth is a dynamic geologic system.

¥ These plate boundaries are the sites of most earthquakes, volcanoes, and young

mountain ranges.

¥ Compared to continental crust, ocean crust is thinner and denser. New ocean crust

continues to form at mid-ocean ridges.

¥ Earthquakes and volcanoes present geologic hazards to humans. Loss of property,

personal injury, and loss of life can be reduced by effective emergency preparedness.

2.1m Many processes of the rock cycle are consequences of plate dynamics. These include

the production of magma (and subsequent igneous rock formation and contact metamor-

phism) at both subduction and rifting regions, regional metamorphism within subduction

zones, and the creation of major depositional basins through down-warping of the crust.

2.1n Many of Earth’s surface features such as mid-ocean ridges/rifts, trenches/subduc-

tion zones/island arcs, mountain ranges (folded, faulted, and volcanic), hot spots, and

the magnetic and age patterns in surface bedrock are a consequence of forces associated

2.1o Plate motions have resulted in global changes in geography, climate, and the pat-

terns of organic evolution.

2.1p Landforms are the result of the interaction of tectonic forces and the processes of

weathering, erosion, and deposition.

2.1q Topographic maps represent landforms through the use of contour lines that are

isolines connecting points of equal elevation. Gradients and profiles can be determined

from changes in elevation over a given distance.

2.1r Climate variations, structure, and characteristics of bedrock influence the develop-

ment of landscape features including mountains, plateaus, plains, valleys, ridges,

escarpments, and stream drainage patterns.

2.1s Weathering is the physical and chemical breakdown of rocks at or near Earth’s sur-

face. Soils are the result of weathering and biological activity over long periods of time.

2.1t Natural agents of erosion, generally driven by gravity, remove, transport, and

deposit weathered rock particles. Each agent of erosion produces distinctive changes

in the material that it transports and creates characteristic surface features and land-

scapes. In certain erosional situations, loss of property, personal injury, and loss of life

can be reduced by effective emergency preparedness.

2.1u The natural agents of erosion include:

¥ Streams (running water): Gradient, discharge, and channel shape influence a

stream’s velocity and the erosion and deposition of sediments. Sediments trans-

ported by streams tend to become rounded as a result of abrasion. Stream fea-

tures include V-shaped valleys, deltas, flood plains, and meanders. A watershed

is the area drained by a stream and its tributaries.

¥ Glaciers (moving ice): Glacial erosional processes include the formation of

U-shaped valleys, parallel scratches, and grooves in bedrock. Glacial features

include moraines, drumlins, kettle lakes, finger lakes, and outwash plains.

¥ Wave Action: Erosion and deposition cause changes in shoreline features, includ-

ing beaches, sandbars, and barrier islands. Wave action rounds sediments as a

result of abrasion. Waves approaching a shoreline move sand parallel to the

shore within the zone of breaking waves.

¥ Wind: Erosion of sediments by wind is most common in arid climates and along

shorelines. Wind-generated features include dunes and sand-blasted bedrock.

¥ Mass Movement: Earth materials move downslope under the influence of gravity.

2.1v Patterns of deposition result from a loss of energy within the transporting system

and are influenced by the size, shape, and density of the transported particles. Sediment

deposits may be sorted or unsorted.

2.1w Sediments of inorganic and organic origin often accumulate in depositional envi-

ronments. Sedimentary rocks form when sediments are compacted and/or cemented

after burial or as the result of chemical precipitation from seawater.