Land-based Landforms

• Continents are the largest areas of land above sea-level. Within each continent are smaller landform structures such as mountains, hills, caves, sand dunes, canyons, valleys, peninsulas, buttes, canyons, capes, cliffs, mountain passes, deserts, plains, isthmuses, mesas, plateaus, prairies, straits, tundras, valleys, calderas and volcanoes. Rock-based landforms surrounded by water are islands, atolls and archipelagos.
  
  

Water-based Landforms

• Seventy percent of the Earth's surface is covered by oceans. Under these oceans are land formations such as mountains, deep trenches, volcanoes and plateaus. On islands and continents are smaller water features such as lakes, waterfalls, rivers, bays, channels, coves, deltas, estuaries, fjords, gulfs, lagoons, marshes, ponds, seas, sounds, swamps, tributaries and wetlands. Glaciers cover 10 percent of the Earth's land, and hold almost 75 percent of the world's fresh water. These massive ice structures have carved mountains, valleys and The Great Lakes of North America. Super-heated geothermal features include hot springs, mud pots, geysers and fumaroles.
  
  

Natural Weather Disasters

• Weather greatly affects the Earth's land and oceans. In the Atlantic Ocean, hurricanes are extremely destructive tropical storms with winds up to 160 mph. These same storms are called typhoons in the western Pacific Ocean, and cyclones in the Indian Ocean and Bay of Bengal. Smaller, but not always less destructive, natural disasters in warmer weather include tornadoes, wind storms, sand storms, severe thunderstorms, mud slides and hail storms. Dangerous winter conditions that negatively affect human populations include blizzards, ice storms, white outs and avalanches. The severity of each weather situation and its impact on lives and property determine if it is a nuisance or a disaster.
  
  

Earthquakes

• Thousands of earthquakes or tremors occur each day worldwide, although most are too small to be felt or do damage. When the Earth's tectonic plates stick, instead of sliding over each other, a tremendous stress builds between the plates. When that stress is released all at once, seismic waves race through rock to the surface of the Earth where the vibrations can be felt. At least 10,000 people die annually because of earthquakes, from crumbling buildings and the resulting mudslides, tsunamis, fires and floods.