unit 2 geography

• how old is the earth


  The Earth is about 4.6 billion years old
• how many time periods is the earth divided? into what are they called?

  Geologists have divided the earth's history in 4 time periods called eras.
• how is an era divided

  Each era is divided by a major event.
• What are the 4 eras of the geologic time scale?

  Precambrian, Paleozoic, Mesozoic, Cenozoic
• Precambrian Era (earliest life)


  4600 million years ago to 570 million years agoShields such as the Canadian shield are formedAccounts for 87% of earth's historyFirst single-celled, and eventually multi-celled organisms are formed
• Paleozoic Era(Permian Period)

  570 million years ago to 245 million years agoLarge parts of North America are covered by shallow seas and located near equatorAppalachian Mountains are formedAmphibians and fish are present, first insectsFirst plants and animals appear on land
• Mesozoic Era (middle life)


  245 million years ago to 66 million years agoFormation of Rocky Mountains beginShallow seas in the interior of North AmericaAge of reptiles such as dinosaursFirst flowering plants, first birds and mammalsMass extinction marks end of the era
• Cenozoic Era (Age of Mammals)


  66 million years ago to presentIce sheets cover much of North AmericaContinents take on present shapeFormations of Rocky Mountains completeHuman beings developThe age of mammals and modern forms of life evolve
• Which era is the longest?What percentage of the Earth's history is this era?

  Precambrian Era. 87%.
• Which era is the shortest?

  Cenozoic Era
• Which era had the dinosaurs?

  Mesozoic era
• Which era saw the first fish and amphibians?

  Paleozoic Era.
• Which era did human beings develop?

  Cenozoic Era
• how many parts is the Crust made up of

  Is made up of 2 parts: Oceanic crust & Continental crust
• Which one is the thicker crust?

  Continental crust
• Mantel


  Largest layer of the EarthMade up of very hot dense rock
• Outer Core


  Composed of nickel and ironSo hot that metals in it are all in a Liquid state
• Inner Core


  Composed of nickel and ironTemperatures and pressure so high that the metals are squeezed together and not able to moveForced to vibrate in place like a solid
• Lithosphere


  The crust and the upper mantle together make up a zone of brittle rock called the LithosphereA solid portion of the earthThis is This is where we live
• The Continental Drift Theory

  German scientist: Alfred Wegener(1915).300 million years ago all earth's land masses were in constant motion and collided to form one supercontinent = Pangaea (means "all land").About 200 million years ago Pangaea started upPieces drifted in different directions to their present positions.
• Four Proofs of the Continental Drift

  - jigsaw fit - fossil evidence-geological evidence-glaciation
• Jigsaw Pieces

  South America and Africa fit together like puzzle pieces
• Fossil Evidence


  There were fossils of the same Plants and Animals on both continents. This could only happen if the continents were once Connected
• Geological evidence

  Mountains that are similar in Age and structure are on both sides of the Atlantic Ocean
• Glaciation


  At one time, Ice sheets covered South Africa, India, Australia, and South America. As these sheets travelled they carved scratches, called Striations into the earth and when the ice melted it left sediment behind.
• Convection Currents


  The earth's plates move because of convection currents: currents created by an uneven distribution of heat from within the Earth.
• Plate Tectonics

  Theory by J. Tuzo Wilson....helps explain most Geologic processes.states that Earth's outer shell is made up of about 20 plates (both continental and ocean).the heat at the earth's core causes the plates to constantly shift.The movement of Earth's plates has shaped Canada in many ways.
• divergent boundary


  Plates pull away from each otherthe Divergent boundary zone. When plates pull apart they create a gap of open space called the Rift zone

  
• transform boundary


  -Plates slide past one anotherPlates may move Horizontally past one another inopposite directions. The place where two plates pass is called a Fault. Erthquake activity is very strong along these plate boundaries.
• convergent boundary


  A plate boundary where two plates move toward each other.
• subduction boundary


  When plates collide, the denser plate is forced down into the mantle (causes a trench)
• 3 different types of Convergent boundaries:

  1. Ocean-ocean (trench)2. Ocean-continent (trench)3. Continent-continent (mountains)
• FOLDING boundary


  When 2 tectonic plates that make up the Earth's crust push together at their border.The extreme pressure forces the edges of the plates upwards into a series of folds
• There are 3 main types of volcanoes:

  Shield VolcanoesCinder cone VolcanoesComposite Volcanoes
• Shield Volcanoes


  Shield Volcanoes are the largest kind of volcanoes on earth.Shield Volcanoes have small eruptions that are not dangerous.When an eruption happens,basaltic lava spreads out in flat layers
• Composite Volcanoes

  Composite: made from two or morematerials with significantly different physical or chemical properties, that when combined, produce a material with characteristics different from the individual componentsFormed by irregular layers of lava and rock fragments.Usually erupt in an explosive way caused by viscous magma.When very viscous magma rises to the surface, it can clog the crater pipe which is near the top causing gas in the crater pipe to get locked up. The pressure will increase resulting in an explosive eruption.
• Cinder Cone Volcanoes


  The most common kind of volcanoeSteep sided cones of basaltic fragmentsSmaller and simpler than composite volcanoes
• Caldera


  A large volcanic crater. Typically one formed by a major eruption leading to the collapse of the mouth of the volcano.
• Lava Tube:


  A natural tube formed by flowing lava which moves beneath the hardened surface of a lava flow.
• Geysers


  Natural fountains that throw up jets of hot water and steam at regular intervals through a vent in the surface.