Class Notes (839,579)
United States (326,038)
Geography (207)
GEOG 2110L (50)


5 Pages

Course Code
GEOG 2110L
David Stanley

This preview shows pages 1 and half of page 2. Sign up to view the full 5 pages of the document.
\VOLCANISM * The processes by which magma and gases are transferred from the Earth’s interior to near or on the surface. * 2 basic types: extrusive vs intrusive volcanism Extrusive: when magma (lava) flows out onto the Earth’s surface and then cools to form igneous rock * volcano: a landform with a vent, or fissure(crack) on the surface which is the end of a conduit originating from below the crust in the Asthenosphere * often a mountain landform (fissures usually do not form features of high relief) * magma originating in theAsthenosphere is expelled through the conduit & out the vent * magma often collects in a magma chamber below the volcano before being expelled * crater: the surface depression at the summit of the volcano * a volcano may be categorized as Active: currently erupting, or has erupted during recorded history Dormant: an active volcano that is in repose but is expected to erupt in the future Extinct: a volcano that is not expected to erupt again * 75% of volcanoes are on the sea floor * most convergent and divergent plate boundaries have high volcanic activity * Hot spots are also areas of high volcanic and earthquake activity * lava: the molten rock issued from a volcano; the term used for magma once it has erupted onto the Earth’s surface * may be two types of material: mafic or felsic * mafic or basaltic lava: high in Mg & Fe, < 50% silica thus less viscous which means it flows readily, and thus less gas is trapped within leading to a less explosive eruption * felsic: richer in silica thus more viscous meaning it flows slower: it is also more acidic, and more gases are trapped leading to more explosive eruptions * pyroclastics or tephra: fragments expelled explosively from a volcano, quite common with felsic magma explosive eruptions) * bombs, pumice, scoria, cinders, lapilli, ash, & dust (Based on size; bombs largest, dust/ash smallest.) ** 2 Types of Eruptions Effusive: * relatively gentle, non-violent eruptions because gases readily escape, thus less explosive * the material issued is primarily mafic magma * if eruption is through a vent, it may form a shield volcano EX: islands of Hawai’i, the Galápagos Islands * if eruption is through a fissure, then it forms a plateau basalt or flood basalt EX: Columbia Plateau in the state of Washington (on land), from mid-oceanic ridges under the water to form sea floor Explosive: * relatively violent eruptions because conduit often gets plugged with cooled/solidified magma, and thus a greater amount of gases are trapped in the magma, increasing pressure * most commonly found along subduction zones * the material issued is primarily felsic magma with a much greater content of pyroclastics * if the eruption is through a vent, this often forms a composite volcano or stratovolcano EX: Mt. St. Helens, Mt. Ranier, Mt. Pinatubo, Mt. Vesuvius ** Other events that may accompany an explosive eruption: * lahar: a flood of ash, mud & water created by melting of snowcap during an eruption or volcanic event EX: one created by the 1985 eruption of Nevado del Ruiz in Colombia killed ~ 23,000 of 25,000 people in the town ofArmero, by covering the town in over 20 ft of mud * nuée ardentes or pyroclatic flow (glowing cloud): a cloud of hot volcanic gas & ash that moves down the flanks of the volcano EX: a flow created during the 1902 eruption of Mont Pelée on the island of Martinique, West Indies annihilated the town of St. Pierre, killing over 30,000 people ** Phreatic eruptions:
More Less
Unlock Document

Only pages 1 and half of page 2 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.