g11. What is volcanism?
Volcanism is the movement of molten materials. Volcanoes are most common on ridges and trenches, but can also be caused by hot spots. Extrusive volcanism is the movement of molten material (lava) on the surface. An active volcano has erupted within the last 200 years, such as Mt. Saint Helens. A dormant volcano has erupted within recorded history, such as Mt. Rainier. An extinct volcano has not erupted within recorded history, such as Devil's Tower. Volcanoes have particular cone shapes. Shield cones have lava that gently oozes out, forming gently sloping sides, like Mauna Loa. Cinder cones typify explosive types of volcanoes with steep sides, which are made of rubble. Krakatoa had the eruption, which was heard thousands of miles away. Paricutin began in a cornfield in Mexico and is the only volcano to be studied from its beginning to its apparent end. Pelé blew out a cloud of fire and poisonous gasses that wiped out a town in minutes. Composite cones are typical of the largest types of volcano. It has alternating layers of debris and lava. Most volcanoes are this type. The crater is the indentation in the top of the cone. Vents are where the lava comes out. The neck is the tube for the lava to escape through. The reservoir is a large holding area for the magma.
Intrusive volcanism is the movement of molten material (magma) beneath the surface of the earth. Batholiths are huge, deep reservoirs of magma that seem to extend down to the mantle. Stocks are smaller batholith-like formations; batholiths are their origins. Laccoliths are mushroom-shaped intrusions of magma. They are the cores of domed mountains. Dikes are formed when magma intrudes vertically across rock layers. Sills are intrusions of magma between rock layers.m12. Why are organisms becoming extinct?
m41. How can matter affect the environment?
m66. How can risks be analyzed?
m74. How is soil important in the environment?
m78. How do droughts and floods impact populations?