Volcanoes
Volcanoes can occur along hot spots, areas where magma moves up through the mantle from the core to the surface forming more crust. Scientists speculate that the magma plumes may reach depths of 1000 miles. The plumes that form Hawaii have unique chemical characteristics that allow geologists to identify the rocks formed by each. The magma is carried upward by convection, a form of heat transfer through a liquid. Hawaii is a series of volcanoes that formed over a hot spot in the Pacific Ocean. The chain of islands has been in motion over the hotspot for 70 million years, 5 million years before the end of the Cretaceous Period. A new island is forming and will emerge from under the sea in several thousand years from now. Volcanoes that form over hot spots are called shield volcanoes.
Hawaii Born of Fire Click here for the Nova guide to the video used in class.
Volcanoes can also occur at the convergence of ocean and continental plates. The dense oceanic plate of basaltic rock sinks below the lighter granitic continental crust. The rock melts into magma. Pressure builds up, and an eruption may take place if the pressure reaches a critical point. The most common type of volcano is the stratovolcano that is formed by alternating layers of lava, ash, and cinders. This forms the familiar cone shape. Volcanic eruptions are usually associated with earthquake activity.
Volcano Simulation Click here to go to a PBS website that shows how volcanoes work.
Volcano Watch- Hawaii Click here for the hotest volcano news on the web. This takes you to the USGS website. Use your browser back button to return here.
Visit Volcano World to see the latest information about active volcanoes world-wide.
To veiw the top ten active volcanoes in real-time and animation, visit Volcano Watch
To learn more about the hazards associated with volcanoes, go to the USGS Volcano Hazards website. There are great diagrams, pictures, and descriptions of different types of hazards.
For a table and diagram showing the connection between earthquakes, volcanoes, and plate movement, Click here.
