Landforms

• Island


  A piece of land surrounded by water on all sides
• Islands


  • Not connected to a continent, but instead are surrounded by water
  • Many are formed by undersea volcanoes
  • A group of islands is often called an archipelago
  • Small islands are sometimes called cays, keys, or islets
• Types of islands


  • Continental islands
  • Oceanic islands
• Continental islands


  Found in seas not far away from the mainland, formed when rising seas cut off part of the land from a continent
• Oceanic islands


  Rise from the sea because of volcanic activity on the ocean floor, when tectonic plates pull apart and lava erupts
• Greenland is the world's largest island and it is mostly covered by a sheet of ice
• Not very many people live on Greenland because it is covered in snow and ice for most of the year
• Peninsula


  A body of land surrounded by water on three sides, connected to the mainland on one side
• Peninsulas


  • Florida
  • Italy
• Lighthouses were often built on peninsulas near the rocky shorelines to warn sailors that they are getting close to land
• Lighthouses were built along the coastline to alert sailors that they are close to land
• Valley


  A long depression or ditch in the Earth's surface, usually lying between ranges of hills or mountains
• Valleys


  • Most are formed by rivers that wear down soil and rock in their path
  • This erosion process can take thousands or even millions of years
  • Valleys high in the mountains are usually V-shaped
• Many cities and towns are built in a valley because it protects people from strong winds and storms
• Canyon


  A very steep and deep "V-shaped" area where a river cuts through the land
• The Grand Canyon is a massive canyon of red rock that is more than 277 miles long and in some spots is 18 miles wide
• The Colorado River has run through the Grand Canyon area for about only 6 million years, carving the rock into the gigantic canyon
• Water leaks into the tiny cracks and holes in the rock walls of the Grand Canyon. As winter comes and the water freezes, it forces the cracks in the walls to expand, causing small pieces of rock to break off and be carried down the river
• Volcano


  A cone-shaped mountain that is formed when lava erupts from a crack in the Earth's surface
• Volcanoes


  • When rock beneath the Earth's surface gets incredibly hot, it becomes liquid rock called magma
  • As soon as the magma erupts and hits the surface, it is called lava
  • Lava is unbelievably hot
  • Ash and chunks of burning rocks spill out from an opening in the Earth
  • Lava will continue to pile up and cool to become very hard igneous rocks
• Types of volcanoes


  • Active
  • Dormant
  • Extinct
• The city of Pompeii was buried in hot ash when Mount Vesuvius erupted thousands of years ago
• Glacier


  A huge block of ice formed when snow does not completely melt away during the summer, and new snow falls on top of the old snow, slowly becoming packed down
• Glaciers take hundreds of years to form
• Most glaciers are found near the north and south poles, and they move very slowly, about 10 feet per year
• Thousands of years ago, gigantic glaciers carved deep spaces into the land and formed the Great Lakes in North America