Where Volcanoes Form Mid-Ocean Ridges –Lava flows out to make crust –Where most volcanic activity takes place Convergent boundaries –During subduction, the temperature and pressure increase causing lava to form Mid-Ocean Ridges –Lava flows out to make crust –Where most volcanic activity takes place Convergent boundaries –During subduction, the temperature and pressure increase causing lava to form

Where Volcanoes Form Hot spots –Not along boundaries –Above columns of rising magma, results of cracks in the crust –Ex. Hawaiian Islands or yellowstone (one of the worlds largest!!) Hot spots –Not along boundaries –Above columns of rising magma, results of cracks in the crust –Ex. Hawaiian Islands or yellowstone (one of the worlds largest!!)

Predicting Eruptions Dormant and Active (not extinct) Monitoring earthquakes Studying volume and composition of volcanic gases Measuring temperature Dormant and Active (not extinct) Monitoring earthquakes Studying volume and composition of volcanic gases Measuring temperature

Goop! Solid when pressure / movement = walk on it Liquid when no pressure / movement = sink

Tectonic Plates Earth’s crust consists of major and minor tectonic plates that move relative to each other.

A Giant Jigsaw Puzzle The lithosphere is made of plates that fit together like a puzzle. Vary in size and thickness. Float on the asthenosphere like ice floats in water. The lithosphere is made of plates that fit together like a puzzle. Vary in size and thickness. Float on the asthenosphere like ice floats in water.

Wegener’s Continental Drift Hypothesis Early 1900’s by Alfred Wegener. Accepted in the 1960s (not that long ago!) Continental drift - continents once formed a single landmass, broke up, and drifted to their present locations. Pangaea existed about 245 million years ago. Evidence is fossil records Early 1900’s by Alfred Wegener. Accepted in the 1960s (not that long ago!) Continental drift - continents once formed a single landmass, broke up, and drifted to their present locations. Pangaea existed about 245 million years ago. Evidence is fossil records

Tectonic Plate Boundaries Three types –Convergent plates collide Destroyed crust! –Divergent: plates separate Growing crust! –mid-ocean ridges –Transform: plates slide horizontally past each other –San Andreas Fault –Earthquakes!! Three types –Convergent plates collide Destroyed crust! –Divergent: plates separate Growing crust! –mid-ocean ridges –Transform: plates slide horizontally past each other –San Andreas Fault –Earthquakes!!