Chapter 17 Plate Tectonics

Structure of the Earth Earth

Drifting Continents  The Earth’s continents move  16 century mapmaker Abraham Ortelius noticed the “fit” of the continents.  19 th century Eduard Sues proposed an ancient landmass named Gondwanaland.  1912 – Alfred Wegener proposed the hypothesis of Continental Drift.

Continental Drift  Wegener proposed that all continents were once joined in supercontinent called Pangea. Pangea  He was one of the first to propose that the continents are drifting on the Earth’s surface. drifting

Continental Drift Evidence  Rock formations (coal beds, sedimentary rocks)  Climate evidence (glacial deposits)  Fossil evidence (same animals)  Shapes of continents  Paleomagnetism – The study of the Earth’s magnetic field history through iron bearing rocks.

Seafloor spreading  In the 1940’s and 1950’s scientists found out that there are mountains in the center of the Atlantic Ocean (Mid-Ocean ridge).  Sea floor spreading occurs at the Mid- Ocean ridge and new land is being formed by volcanoes. Sea floor spreading Sea floor spreading  Scientists used a magnetometer to find that magnetic reversals occur on Earth. magnetic reversals magnetic reversals  Another view of magnetic reversals view

Seafloor Spreading  Scientists also found that there is more sediment on the sea floor as you move away from the Mid-Ocean ridge.  Scientists map the age of the rocks on the ocean floor with isochrons.  An isochron is line on a map that connects points that have the same age.

The Missing Link  Sea floor spreading explains how the continents move across the surface.  The plates (the rigid mantle) slide across the Asthenosphere.

Plate Tectonics  Theory of Plate Tectonics states that Earth’s crust and rigid upper mantle are broken into enormous slabs called plates.  There about 12 major plates, and some smaller plates.  These plates interact at plate boundaries.

Plate Tectonics  Major unifying Geology theory that explains:  Volcanoes  Mountain ranges  Mid-Atlantic ridge and rift valleys  Trenches  Island arcs  Continental Drift  Show video Fearless Planet - last chapter

Look see Look see

Current continents

Plate boundaries

Future continentsFuture continents? Future continents

Earthquakes & Volcanoes

Growth of a continent  Subducting plates Subducting plates Subducting plates  Crashing continents Crashing continents Crashing continents  View video Mountains:  Ethiopian Highlands  Andes  Rockies in summer  Alps

Hotspot

Ridge

Trench

Plate Movements  Volcanism Volcanism  Plate movement Plate movement Plate movement  Inside the Volcano  Ring of Fire  Ocean Deep  Ocean Vents  Inside the Volcano  Iceland