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• Continental Drift


  Alfred Wegener's hypothesis, now accepted, of the movement of continental land masses; at one time all continents were joined together in a single land mass, called Pangea
• Fossils found on different continents


  • Similar plants and animals
• Wegener discovered geologists had found similarities in rocks on both sides of the Atlantic Ocean
• A mountain range, called the Appalachians, in eastern North America was made of the same kind and ages of rock as the mountain range that ran through Britain and Norway
• Glossopteris Fossils


  • Plants that resembled ferns, lived about 250 million years ago, their seeds could not have traveled across the ocean
• Folded mountains


  • Sedimentary rock layers that are tilted at an angle, or even vertically to form mountains
• Glacial deposits


  • Scratches in the rocks show that glaciers once covered this land
• Coal deposits


  • Ancient tropical forests produced these coal deposits, which seem to have once been connected
• Trenches


  Deep valleys on the ocean floor
• Ridges


  Mountain chains that rise from the ocean floor
• The Mid-Atlantic Ridge stretches from north to south along the middle of the Atlantic Ocean
• Geothermal Activity


  Water that is heated by hot magma a few kilometres below the surface; produces hot springs and geysers
• Theory of Plate Tectonics

  The idea that the continental crust is broken up into large areas called plates; all plates are moving very slowly in various directions
• Plates


  Continental and oceanic crust
• Boundary


  Edge or location where plates meet
• Diverging Boundary


  Edge or location where the continental plates are moving apart. One example is the Mid-Atlantic Ridge on the floor of the Atlantic Ocean
• Converging Boundaries


  Edge or location where continental plates come together
• Subduction


  Collision between the oceanic and continental plates where the dense, heavy ocean plates slides below the lighter continental plate
• Transform Boundary


  Edge or location where continental plates slide along beside each other; earthquakes are caused when plates bind. An example is the San Andreas Fault on the west coast of the United States
• Mountain


  Part of Earth's surface that is much taller than the land around it. Mountains form in places where plates collide
• Mountain Range


  Series of mountains
• Mountain building


  Process of creating mountains
• Folds


  Bends in rock layers; most mountains were created by a combination of folding and faulting
• Anticline


  The upward or top part of the folded rock
• Syncline


  The bottom of the fold
• Faults


  Large cracks in the rock; most mountains were created by a combination of folding and faulting
• Thrust blocks


  When sedimentary rock is squeezed from the sides, it can form into slabs that move up and over each other like shingles on a roof
• Over thrust mountains


  Huge amounts of rock that can form when tectonic forces stretch Earth's crust and fault blocks tilt or slide down, with older rock ending up on top of younger rock
• Fossils


  Traces of once-living things that are preserved in rocks
• How a fossil develops

  1. Sediments quickly bury the original plant or animal remains

  2. A cavity is created as the original organic form decays, which can then be filled by other sediments

  3. The original organism is slowly replaced by mineral crystals
• Trace fossil


  A cavity or track left behind by an organism, for example a footprint
• Cast fossil


  Filled in cavities left by the original organic bodies
• Paleontologist


  Scientists who study early life forms from animal and plant fossils
• Strata


  Layers formed by sediment over millions of years
• The fossils record found in rocks shows a sequence, but not one based on size, habitat, or shape. Rather, the fossil record shows a sequence of different life forms appearing through time
• Rock formations are deposited in layers from the oldest on the bottom to the youngest at the top. Paleontologists use these layers, or geological columns, to help determine the age of the fossils they find
• The Burgess Shale Fossil Beds have preserved the soft tissue of many species, allowing scientists to study these specimens in detail. Fossils look much the same as they did a half billion years ago
• Eras


  Geologic time intervals; based on the sequence of rock strata and the different life forms
• Scientists estimate that Earth is about 4.6 billion years old
• Precambrian Era


  4600 to 600 millions of years ago. The first simple organisms and first soft-bodied animals appeared during this era