Bellringer 10/31/16 Make a Cornell notes data sheet. Don’t write the types of matter and solids, liquids, gases…. Etc…

17.1 Continental Drift

Background Maps! Explorers, such as Columbus and Magellan, began to sail the earth and brought back information that was made into maps These maps showed a curious outline. The edges of the continents looked like they should fit together like a puzzle!

Continental Drift Alfred Wegener- first proposed hypothesis Early 1900s Published The Origin of Continents and Oceans Pangaea = “all lands” Panthalassa = “all seas”

Continental Drift Super-continent, Pangaea, began breaking apart 200 million years ago, Mesozoic Era Continents “drifted” to current positions Continents “broke” through the ocean crust Crumpled to cause mountains

Evidence 1. Jigsaw puzzle – how the continents fit together

Evidence 2. Fossils Mesosaurus (dinosaur), Glossopteris (plant) Found at the edges of two vastly separated continents

Evidence 3. Ancient climates Areas that have glaciers today show evidence of being near the equator at one time. The coal fields in Kentucky formed in a tropical area.

Evidence 4. Rock Types Similar rock types on continents on opposite sides of the Atlantic Ocean. Similar, age, structure and rock types are found in the Appalachian Mountains and mountains in Scotland and Scandinavia.

Rocks When the continents are reassembled, the mountain chains from a continuous belt

Proved? Wegener was unable to provide mechanism to prove hypothesis Evidence now Paleomagnetism Earthquake patterns Ocean drilling Hot spots

Evidence Today Mid-Atlantic Ridge Undersea mountain range Scientists brought rocks up from the ocean floor Much younger than the rocks from the continent Oldest oceanic rock = 175 million years old Oldest continental rock = 4 billion years old

Evidence Mid-Atlantic Ridge Hess proposed hypothesis At the center is a break, or rift, in the crust The rift is moving apart Trenches = deepest parts of the ocean The deepest trench, the Marianas Trench, is more than 11 km deep

Evidence Seafloor spreading Molten rock (magma) seeps through forming new ocean crust Dietz gave it the name

Evidence Paleomagnetism the Earth’s magnetic field switches orientation Produces magnetic “stripes” in the new rock along the ocean floor

Paleomagnetism As magma solidifies to form rock Magnetic field aligns and becomes permanent Normal polarity points North Reverse polarity points South

Paleomagnetism Some rocks showed reverse polarity Scientists discovered periods of reversed magnetic field on Earth Patterns on ocean floor Mirror images

Plate Tectonics The evidence supporting Continental Drift has caused scientists to look more at what makes up the Earth This thinking takes us to Plate Tectonics

In-Class Assignment/Homework