1. 6 th grade science

2.  Geologists plot earthquakes on maps to analyze patterns in the data.  www.earthquakes.usgs.gov/earthquakes. www.earthquakes.usgs.gov/earthquakes  An Earthquake is the shaking or trembling of the Earth due to the movement of tectonic plates.  Magnitude is the amount of energy released by an earthquake; magnitude relates to the Strength of an Earthquake.

3.  About 20 earthquakes each day are recorded.  (Nothing less than a 2 is recorded).  About 9,000 very minor (below a 3) earthquakes occur daily.

4.  Yearly about:  130,000 earthquakes between a 3- 3.9  13,000 earthquakes between a 4- 4.9  1,300 earthquakes between a 5-5.9  130 earthquakes between a 6 -6.9  17 earthquakes between a 7- 7.9  1 earthquakes between a 8 +  This is Amazing stuff!!

5.  Suggest all continents were once connected  ( Pangea)  Evidence- The continents fit like a puzzle and the same fossils have been found on continents separated by an ocean.

6.  Describes the motion of Earth’s plates. Tectonic plates are thick moving slabs of rock. They include the crust and upper most solid part of the mantle (called the lithosphere).  The plates are in constant motion due to hot convection currents produced by the molten rock(magma) in the mantle.

7.  The plates move only a few centimeters each year.  The plates can move into one another, away from one another, or across one another.

8.  The interaction of plates changes Earth’s surface through earthquakes, volcanoes, tsunamis, trenches, and mountains.

9.  It is at plate boundaries where most earthquakes and volcanoes occur.

10.  Divergent  When 2 continental plates move apart a deep valley rift forms( new crust results).  Look at page 45

11.  Sea Floor Spreading  When 2 ocean plates spread apart, a mid- ocean ridge forms(new crust). Molten material rises from convecting mantle and erupts.  The molten material hardens and pushing older rock to the side. (page 45).

12.  Convergent-Oceanic/Continental  When an ocean plate and Continental plate collide, the ocean plates will slide under the harder, less dense continental plate.  Mountains result( possibly volcanoes).

14.  Convergent-Continental/Continental  The collison of 2 continental plates results in the formation of Mountains.

15.  When 2 ocean plates collide, one slide under the other and part of the rock melts. The molten rock rises through the cracks/ holes forming volcanic eruptions.

16.  Transform  When 2 continental plates against each other, the rubbing and friction create great pressure. An earthquakes results! ( pg.44)

18.  Earthquakes, mountains, and volcanoes most often occur at the boundaries or Earth’s tectonic plates.

19.  Most of the plates that are moving apart are found at the bottom of the ocean. New oceanic crust forms as magma rises to the ocean floor. The longest mountain range in the world, the Mid-Atlantic Ridge, was formed this way.

20.  When two continental plates bump into each other, they fold up. The Himalayan Mountains were formed when India slammed into the Asian plate about 50 million years ago.

21.  When a land plate (granite) collides with an ocean plate(basalt), the oceanic crust slides under the land(basalt is less dense than granite). As it sinks some of it melts into molten rock. The molten rock comes up through the crust creating a volcano.

22.  When 2 oceanic crusts collide, one plate slides under the other causing the formation of a trench(deepest part of the ocean) as well as underwater volcanoes. Underwater volcanoes may some day rise above the water and become islands.

23.  Plates can rub against each other along a fault line. Sometime they stick as they grind past one another. Great stress and pressure builds up; when it becomes too great, the rocks move causing great vibrations, Earthquakes.

24.  The three types of plate boundaries and movement.  Convergent boundaries- 2 plates moving together and forming mountains or volcanoes.  Divergent boundaries- 2 plates spreading apart, forming rift valleys or mid-ocean ridges- new crust is formed.  Transform Boundaries- 2 plates that slide past each other releasing energy in the form of earthquakes (caused by pressure).

25.  A magnet is a material that has the ability to attract iron, steel, nickel, and cobalt.  Metals that are attracted to a magnet have the ability to become magnetized themselves( their atoms can be aligned).  The atoms in a magnet are aligned.  A magnet can make another object a temporary magnet. Rub the object repeatedly in the same direction with a magnet and the atoms will become organized (aligned).

26.  The poles are the strongest part of a magnet. Each magnet has a north and a south pole.  Opposites attract! Like Poles repel!  North >South Attract  South/South or North/North repel (push or pull).  The magnetic field is the magnetized area surrounding a magnet.

27.  The Earth is a giant magnet. It is very similar to a bar magnet.  Scientists believe that Erath’s magnetic field is due to electrical currents produced by convection and rotation of the liquid outer core and inner most layer of mantle.  The motion of the liquid creates an electrical current that causes Earth to behave like a magnet.

28.  The Earth has a magnetic north and south pole. The Earth’s magnetic field attracts materials that are magnetized.  The needle of a compass is a magnet so it has a north and south pole.  The colored end of the compass needle is “north seeking” so it is attracted to Earth’s “magnetic north”( which is slightly different from Earth’s geographic North pole.)

29.  When travelers can tell which way is north (by the needle on the compass pointing north) they can easily identify south, east, and west.

30.  Fossil evidence leads scientists to believe that the continents were one large land mass (Pangea) hundreds of millions of years ago.

31.  Sedimentary rocks are formed when sediments and plants and animal remains pile up and under great pressure, cement together.  The oldest rock layers are on the bottom and the newest are on top.

32.  Over millions of years as Earth changed, the swamps, lakes, and seas became land masses. Scientists have been able to find fossils within sedimentary rock to learn Earth’s history.  Some of the fossils from the continent to continent were of the same species of plant and animal. This provides support for the theory of continental drift.

33.  Formed in several different ways:  Most fossils form when a plant or animal dies and is buried by sediment which hardens over the years into rock.  A mold or cast forms when the hard parts of the organism are buried in the sediment.  Petrified fossils, such as wood, are fossils in which minerals replace all or part of an organism.

34.  Trace Fossils provide evidence of the activities of ancient organisms. Foot prints provide clues of an animals size (dinosaurs!) and behaviors/activities.  Preserved fossil remains have little or no change due to being preserved in sap, tar, or ice.  Carbon film- a thin coating of carbon is left behind on rock preserving the delicate parts of leaves and insects.

35.  Geologists can learn:  The age of the fossils  Evidence of the types of plants/animals that were once in an area.  Changes in climate and other environmental conditions of an area( such as the presence of ocean organisms lead us to the conclusion that some land areas were once an ocean)

36.  The Earth has a very long history (4.6 billion years). Scientists learn about major events in the history of the earth by using rocks, rock layers, and fossils.  The fossils in some layers of rock can be used to determine the relative age of different rock layers(its age compared to other rocks).  Law of superposition: in undisturbed rock, the oldest layers are the lowest layers(oldest). The youngest are on top.

37.  A gap in the geological record, usually caused by erosion of old rock layers and the deposition of new rock layers.

38.  All matter is made of atoms; if the atoms are the same, the matter is an element( elements include: carbon, oxygen, iron, lead and potassium.  The rate of decay is an element's half- life. The half-live is the time it takes for half of the radioactive atoms to decay.

39.  Geologists use the geologic time scale to show Earth’s History.  Geological time begins with the Precambrian Period(88% of history) or the earth is 4.6 billion so 544 million years ago.  Between the Precambrian Period and now, there are 3 long eras(ages): Paleozoic, Mesozoic, and Cenozoic.