A Meticulous Perspective...

  Forces inside the earth’s mantle and near its surface push, stress, and deform rocks. At some point the stress can cause the rocks to suddenly shift or break and produce a transform fault, or fracture in the earth’s crust. When a fault forms, or when there is abrupt movement on an existing fault, energy that has accumulated over time is released in the form of vibrations, called seismic waves , which move in all directions through the surrounding rock. This internal geological process is called an earthquake .  Most earthquakes occur at the boundaries of tectonic plates , when colliding plates create tremendous pressures in the earth’s crust or when plates slide past one another at transform faults. The place where an earthquake begins, often far below the earth’s surface is called the focus . The earthquake’s epicenter is located on the earth’s surface directly above the focus. The energy of the earth’s tremendous internal stress is released in the form of seismic (shock) waves, wh

  Forests provide highly valuable ecological and economic services. For example, through photosynthesis, forests remove CO2 from the atmosphere and store it in organic compounds (biomass). By performing this ecological service as a part of the global carbon cycle, forests help to stabilize average atmospheric temperatures and slow projected climate change. Forests also provide us with oxygen, hold soil in place, and aid in aquifer recharge and flood control. Scientists have attempted to estimate the economic value of this and other ecological services provided by the world’s forests and other ecosystems. ECOLOGICAL SERVICES PROVIDED BY FORESTS: Support energy flow and chemical cycling. Reduce soil erosion. Absorb and release water. Purify water and air. Influence local and regional climate. Store atmospheric carbon. Provide numerous wildlife habitats. ECONOMICAL SERVICES PROVIDED BY FORESTS: Fuelwood Lumber Pulp to make paper Mining Livestock grazing Recreation Jobs

  Forests are lands dominated by trees. The three main types of forest—tropical, temperate, and cold (northern coniferous, or boreal)—result from combinations of varying precipitation levels and varying average temperatures. 1. TROPICAL FORESTS: Tropical rain forests are found near the equator, where hot, moisture-laden air rises and dumps its moisture. These lush forests have year around, uniformly warm temperatures, high humidity, and almost daily heavy rainfall. This fairly constant warm and wet climate is ideal for a wide variety of plants and animals. These forests are often called jungle, but that word refers to the thickest and most dense parts of a tropical rain forest. Tropical rain forests have a very high net primary productivity. They are teeming with life and possess incredible biological diversity. Although tropical rain forests cover only about 2% of the earth’s land surface, ecologists estimate that they contain at least half of the earth’s known terrestrial plant and a

  Grasslands occur mostly in the interiors of continents in areas that are too moist for deserts to form and too dry for forests to grow. Grasslands persist because of a combination of seasonal drought, grazing by large herbivores, and occasional fires—all of which keep shrubs and trees from growing in large numbers.  The three main types of grassland—tropical, temperate, and cold (arctic tundra)—result from combinations of low average precipitation and varying average temperatures. 1. TROPICAL GRASSLAND: One type of tropical grassland, called a savanna, contains widely scattered clumps of trees such as acacia, which are covered with thorns that keep some herbivores away. This biome usually has warm temperatures year-round and alternating dry and wet seasons. Tropical savannas in East Africa are home to grazing (mostly grass-eating) and browsing (twig- and leafnibbling) hoofed animals, including wildebeests, gazelles, zebras, giraffes, and antelopes, as well as their predators such as

  In a desert, annual precipitation is low and often scattered unevenly throughout the year. During the day, the baking sun warms the ground and evaporates water from plant leaves and the soil. But at night, most of the heat stored in the ground radiates quickly into the atmosphere. Desert soils have little vegetation and moisture to help store the heat and the skies above deserts are usually clear. This explains why in a desert you may roast during the day but shiver at night. The lack of vegetation, especially in tropical and polar deserts, makes them vulnerable to sandstorms driven by winds that can spread sand from one area to another. Desert surfaces are also vulnerable to disruption from vehicles such as SUVs. A combination of low rainfall and varying average temperatures creates tropical, temperate, and cold deserts. 1. TROPICAL DESERTS: Tropical deserts such as the Sahara and the Namib of Africa are hot and dry most of the year. They have few plants and a hard, windblown surfac

Water pollution is any change in water quality that can harm living organisms or make the water unfit for human uses such as irrigation and recreation. It usually involves contamination by one or more chemicals or excessive heat (thermal pollution).  Sources: Water pollution can come from a single (point)source, or from a larger, more dispersed (nonpoint) source.  Point sources discharge pollutants into bodies of surface water at specific locations through drain pipes, ditches, or sewer lines. Examples include factories, sewage treatment plants (which remove some, but not all, pollutants), underground mines, and oil tankers. Because point sources are located at specific places, they are fairly easy to identify, monitor, and regulate. Most of the world’s more-developed countries have laws that help control point-source discharges of harmful chemicals into aquatic systems. In most of the less-developed countries, there is little control of such discharges. Nonpoint sources are broad a

Hydropower uses the kinetic energy of flowing and falling water to produce electricity. It is an indirect form of solar energy because it is based on the evaporation of water, which is deposited at higher elevations where it can flow to lower elevations in rivers as part of the earth’s solar-powered water cycle. The most common approach to harnessing hydropower is to build a high dam across a large river to create a reservoir. Some of the water stored in the reservoir is allowed to flow through large pipes at controlled rates to spin turbines that produce electricity. Hydropower is the world’s leading renewable energy source used to produce electricity. The use of microhydropower generators may become an increasingly important way to produce electricity. These are floating turbines, each about the size of an overnight suitcase. They use the power of flowing water to turn rotor blades, which spin a turbine to produce electric current. They can be placed in any stream or river without