Lecture: Tectonic Plates

He proposed Continental drift so the idea that maybe the continents fit together

Jigsaw puzzle fit Matching fossils across continents Geologic features Paleo-environmental proxies

The idea that the continents including their shelf fit with each other

The idea that there were fossils found of the same animal on different continents, but there are zones where you find the animal and nowhere else So, the continents would have needed to be connected for them to be on both continents

There are a lot of similarities in the mountain ranges in North America, Africa, and Europe So, they were probably once connected

The idea of looking at the climate and seeing remnants of glaciers and the type of climate remnants

Wegener proposed that continents plow through ocean crust like an ice-breaker ship Most researchers thought probably not since the continents are not strong enough relative to the oceanic crust and would undergo greater deformation

Harry Hess kept his sonar on the whole time to collect data during WWII

The measurement of the depth of water in oceans, seas, or lakes

Marie tharp See the discovery of mid-ocean ridges with rift valleys

Hess proposed a model of seafloor spreading to explain the features in Tharp’s map The idea of divergent with the mid-ocean ridge as the spreading center Having magma coming out and solidifying by the mid-ocean ridge The older oceanic crust sink down as they cool off with higher density

Mapping Earthquakes Seafloor sediment Seafloor age Seafloor magnetic reversals Age of Island Chains

Earthquakes shallow along mid-ocean ridges Deep near trenches

The thickness of sediments increases with increasing distance from the ridge crest The age of the seafloor also increases from distance from the mid-ocean ridge which makes sense since it has had more time for sediment to deposit

The seafloor is older as you get farther from the mid-ocean ridge Yet no seafloor older than 180 myr but why is there no old seafloor The oceanic crust/sea floor must subduct

We see that there are magnetic stripes parallel to the spreading center and alternate with each other way and switch Symmetrical on both sides of the ridge

A lot of island chains are young and some are underwater

Plates contain continents and ocean floor, move together on top of a fluid asthenosphere

Old oceanic crust sinks back into the mantle at ocean trenches (slab pull) New oceanic crust is created at the mid-ocean ridge (ridge push)