Summary
Matter that forms the outer layers of the Earth follows many cycles, driven by the energy of the Sun and the Earth's inner heat energy. The atmospheric cycle of the weather redistributes solar energy from the warmer equatorial regions to higher latitudes through the development of global convection cells of air. The prevailing westerly flow of weather across North America marks one of these large cells, while the jet stream delineates the boundary between this flow and the contrary cell to our north. Climate, in our contrast to weather, varies much more slowly in response to ocean circulation, the Sun's energy output, the positions of continents and mountain ranges, and other relatively fixed conditions.
The hydrologic cycle traces the path of water as it evaporates from the ocean, falls back to Earth as rain, and forms lakes, rivers, ice caps, glaciers, and groundwater reservoirs. During unusually cold climatic periods, more water falls as snow, creating white reflective blankets that further reduces the amount of absorbed solar radiation. This situation, if prolonged can lead to an ice age, during which ocean level drop significantly and great sheets of ice cover the land at high and middle latitudes. Temperatures in these latitudes may be moderated, however, by ocean currents that are important in redistributing temperatures at the Earth's surface.
The solid materials of the Earth's crust are subject to the rock cycle. The first rocks to form on the cooling planet were igneous rock, which form from hot, molten material. Volcanic or extrusive igneous rocks solidify on the surface, while intrusive igneous rocks cool underground. The first igneous rocks were subjected to weathering by wind and rain, which eventually produced layers of sediment and the first sedimentary rocks. Sandstone's, shales limestone's and other sedimentary rocks are deposited in ocean basins, layers upon layer, in sequences often many kilometers thick. Igneous and sedimentary rocks were subsequently buried and transformed by the Earth's internal temperature and pressure to form metamorphic rocks. Each of the three major rock types —igneous, sedimentary and metamorphic—convert into the others by the ongoing process of the rock cycle.
