Developing the Theory of Plate Tectonics! The Game

Mapping The Ocean Floor After WWII scientists began exploring the seafloor in greater detail. They were able to determine the depth of the ocean using a device called a(n): Echo Sounder

Mapping The Ocean Floor Scientists used the Echo Sounder to determine the depth of the ocean floor. They used this data to create a(n) ______________ map of the sea floor Topographic

Mapping The Ocean Floor These new topographic maps of the seafloor revealed that vast mountain ranges stretched for many miles deep below the ocean’s surface. The mountain ranges in the middle of the oceans are called _____________________ ridges Mid-ocean

Seafloor spreading Seafloor Spreading By the 1960’s scientists discovered a new process that helped explain continental drift. __________________ is the process by which new oceanic crust forms along a mid-ocean ridge and older oceanic crust moves away from the ridge. Seafloor spreading

When the seafloor spreads, the mantle below melts and forms _________ Seafloor Spreading When the seafloor spreads, the mantle below melts and forms _________ magma

Seafloor Spreading Because magma is [more/less] dense than solid mantle, it rises through the cracks in the crust along the mid-ocean ridge

When magma erupts on Earth’s surface it is called: Seafloor Spreading When magma erupts on Earth’s surface it is called: lava

Basalt Seafloor Spreading As this lava cools and crystallizes on the seafloor, it forms a type of rock called ________ Basalt

Pillow lava Seafloor Spreading Because the lava erupts into water, it cools rapidly and forms rounded structures called ______________________. Pillow lava https://www.youtube.com/watch?v=DdIUuUY0L9c

Mid-ocean ridge Seafloor Spreading As the seafloor continues to spread apart, the older oceanic crust moves away from the _________________ where new crust is being formed. Mid-ocean ridge

Next to the mid-ocean ridge Seafloor Spreading Where can the youngest oceanic crust be found? Next to the mid-ocean ridge

Wegener Seafloor Spreading The idea that seafloor spreading that explains continental drift was proposed by: Wegener

Topography of the Seafloor The mid-ocean ridge system can form in 2 different ways. What are these? 1) Large amounts lava erupt from Center of ridge, cool and build up around ridge 2) As lava cools and forms new crust it cracks The rocks move up or down along these cracks In the sea floor forming jagged mountain ranges

Topography of the Seafloor Why is it much flatter further away from the mid-ocean ridge Sediment settles on sea floor

Topography of the Seafloor The theory of seafloor spreading provides a way to explain what? How continents move

outer Magnetic Reversals Recall that the iron-rich, liquid __________ core is like a giant magnet. outer

Normal Polarity Magnetic Reversals Today’s magnetic field is described as having __________________ - a state in which magnetized objects, such as compass needles, will orient themselves to point north Normal Polarity

Magnetic Reversals A state in which magnetized objects would What is reversed polarity? A state in which magnetized objects would reverse direction and orient themselves To point south

Hundred thousand, million Magnetic Reversals Magnetic reversals occur every few _____________ to every _________ years Hundred thousand, million

Rocks Reveal Magnetic Signature ________ on the seafloor contains iron-rich minerals that are magnetic. Each mineral acts like a small magnet! Basalt

Rocks Reveal Magnetic Signature Magnetic minerals align themselves with Earth’s magnetic field. When lava erupts from a vent along a mid-ocean ridge, it cools and ___________ Crystallizes

Evidence to Support the Theory How did scientists prove the theory of seafloor spreading?