Plate Tectonics: Reshaping Earth's Story

Plate Tectonics: Reshaping Earth's Story

Understanding Earth's Dynamic Surface How Continental Movement Shaped Our Planet Year 10 Earth Science

What Makes Earth's Surface Change?

Think about natural disasters you've heard about Mountains, valleys, and ocean trenches How do continents move over millions of years?

Before Plate Tectonics: Old Ideas About Earth

Earth was thought to be static and unchanging Mountains formed by Earth 'shrinking' as it cooled Continents were fixed in their positions No explanation for similar fossils on different continents

Alfred Wegener: The Pioneer

German meteorologist and geologist (1880-1930) Proposed Continental Drift theory in 1912 Noticed continents fit together like puzzle pieces Collected evidence but couldn't explain the mechanism

Wegener's Evidence for Continental Drift

Scientific Rejection

'It is wrong to assume that continents can move through ocean floors like ships through water.' - Leading geologist's response to Wegener's theory The problem: No mechanism to explain how continents could move

The Missing Piece: Seafloor Spreading

Harry Hess proposed seafloor spreading (1962) New oceanic crust forms at mid-ocean ridges Older crust moves away from ridges Oceanic crust eventually sinks back into Earth

Modeling Seafloor Spreading

Imagine a piece of paper emerging from a crack in your desk The paper represents new oceanic crust As more paper emerges, older sections move away Eventually, the paper disappears into another crack

Evidence for Seafloor Spreading

Magnetic striping on ocean floor Youngest rocks at mid-ocean ridges Oldest rocks at continental margins Symmetrical patterns on both sides of ridges

Birth of Plate Tectonic Theory

Combined Continental Drift and Seafloor Spreading Earth's surface divided into large plates Plates move due to convection in the mantle Explains earthquakes, volcanoes, and mountain building

Major Tectonic Plates of the World

Types of Plate Boundaries

{"left":"Divergent: Plates move apart, new crust forms\nConvergent: Plates collide, crust destroyed or deformed","right":"Transform: Plates slide past each other horizontally"}