Unit 6: Earth Shaped from the Outside in. Cycle 18: Volcanism & earthquakes Cycle 19: Plate Tectonics Cycle 20: Weathering & Erosion. Connection to last unit….
Cycle 18: Volcanism & earthquakes
Cycle 19: Plate Tectonics
Cycle 20: Weathering & Erosion
-Low angle slopes of 1-10
-Generally on ocean floor
-made of basalt lava flows, no ash or pyroclastics
-basaltic magma, low gas trapping
Steeper slopes 10-25, taller than cinder cones. Smaller in height and width than shield volcanoes
Cascades (Mt. St. Helens), Andes
Volcanoes on continents over ocean-land subduction zones
Alternating Explosive/quiet eruptions
Built up by alternating layers of lava and pyroclastics
Built over tens to hundreds of thousands of years
Andesitic (or Granitic) composition magma, gas rich
Smallest volcanic features have large craters with steep slopes of 30-40
Generally forms on continents
Built of pyroclastics (tephra/cinders) not lava flows.
Generally short lived eruptions - weeks to a few years until the magma is degassed, then it solidifies in the pipe and flows form from the base
Paricutin, Mexico, cinder cone soon after its birth in 1943 in a Mexican cornfield.