Core Concepts – The Water Cycle & Groundwater
1.2g. Earth has continuously been recycling water since the outgassing of water early in its history. This constant recirculation of water at and near Earth’s surface is described by the hydrological (water) cycle.
> Water is returned from the atmosphere to Earth’s surface by precipitation. Water returns to the atmosphere by evaporation or transpiration from plants. A portion of the precipitation becomes runoff over the land or infiltrates into the ground to become stored in the soil or ground water below the water table.
> The amount of precipitation that seeps into the ground or runs off is influenced by climate, slope of the land, soil, rock type, vegetation, land use, and degree of saturation.
> Porosity, permeability and water retention affect runoff and infiltration. Soil capillarity influences this process.
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 use of contour lines (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 development 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 surface. 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 landscapes. 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 transported by streams tend to become rounded as a result of abrasion. Stream features 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, including 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.
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 hurricanes, monsoons, rainy and dry seasons, flooding, severe weather, and ozone depletion.
