Presentation on theme: "Our Changing Earth. What is a Theory? In science, its almost the same as a fact Must be some sort of evidence to support a theory Even with evidence there."— Presentation transcript:
Our Changing Earth
What is a Theory? In science, its almost the same as a fact Must be some sort of evidence to support a theory Even with evidence there is still debate about how true it is
Continental Drift Theory Alfred Wegener said the world used to be one large land mass millions of years ago The land was called Pangaea Pangaea kept moving apart a few centimeters each year After millions of years it became the world we see today
Continental Drift Theory Evidence for Continental Drift includes Continental Edges Same Fossils Climate Rock Structures Puzzle Pieces On different continents Continental ice sheets Mountains with similar features fit like found seen in evidence from showed
Plate Tectonics Plate Tectonics – a more advanced theory about how the continents move Explains that there are loose plates in the earth that shift causing: –Oceanic Trenches –Mountains –Volcanoes –Earthquakes.
How Do the Plates Move? g/17457/english.html
So… Continental Drift – theory that says continents drift around on plates Plate Tectonics – theory that explains WHY scientists believe the continental drift theory is true
Now its time for a…
What is Continental Drift? Theory that says the continents are moving on plates
What is Plate Tectonics? Theory that explains WHY scientists think continental drift occurs It tells us how the earths plates move
Divergent Boundaries This is when the plates move apart It happens mostly between oceanic plates The rising magma causes volcanoes and underwater mountains to be formed
Convergent Boundary When the two plates are in the OCEAN they collide and form deep trenches. When the two plates are on the CONTINENTS they collide to form mountains.
Transform (Sliding) Boundaries This is when the plates slide past each other or move horizontally The sliding is what causes earthquakes This type of boundary is found in California