VOLCANISM- Chapt.18 Flashcards
Describes all the processes associated with discharge of magma, hot fluids, and gasses.
Volcanism
Two places volcanisms can occur.
Above ground or Underwater
An opening in a planet or moon’s crust through which molten rock, hot gasses, and other materials erupt.
Volcano
Scientists who study eruptions, lava, magma, and the conditions under which these form.
Volcanologist
Fissures on the seabed from which geothermally heated water discharges
Hydrothermal Vent
Two types of volcanism.
Convergent, Divergent
Definition of Convergent volcanism.
When the oceanic plate sinks, part of it melts and rises up the continental plate because the magma is less dense than the surrounding material. It mixes with other solids as it rises until it reaches the surface and forms a volcano.
Definition of Divergent volcanism.
When plates separate, the magma between fills the empty space and makes pillow shaped lava at ocean ridges. The lava from divergent volcanism tends to be non explosive and comprises two-thirds of Earth’s volcanism since it spews lava at a constant rate.
-Unusually hot regions of Earth’s mantle where high temperature magma rises. Some of these volcanoes end up becoming dormant bec. over time, the plates move and the hot spots move away from where the volcano formed
-Over land= flood basalts, plateaus
-Over water= islands(often volcanic, like Hawaii)
Hotspots
Volcano Anatomy: Enumerate Everything.
*Ash and Gas Cloud- airborne particles emitted by the volcano.
*Main Vent-main exit point of lava
*Parasitic Cone-cone-shaped accumulation of volcanic material not part of the central vent of a volcano.
*Lava-magma that has reached the surface.
*Throat-where the lava comes out from right before the vent.
*Secondary Vent-secondary openings where magma erupts.
*Sill-planar sheet of magma which is parallel to the surrounding rock.
*Conduit-an underground passage which magma travels through.
*Magma Chamber-large pool of liquid rock beneath the surface of the Earth.
*Magma- molten rock beneath the earth.
OTHER PARTS:
*Crater-circular depression on the top of the volcano.
*Caldera- bigger crater usually found after a volcano has erupted.
Types of Magma
*BASALTIC- Has less than 50 percent silica and is not very reactive with sediments. Its low silica content produces low-viscosity magma and the resulting volcano is characterized by quiet eruptions.
*ANDESITIC- Has 50-60 percent silica and is found along oceanic-continental subduction zones. The higher silica content gives it intermediate viscosity which also gives it intermediate explosive properties.
*RHYOLITIC- Has more than 60 percent silica and is found in the overlying continental crust rich in silica and water. Its high viscosity and large volume of dissolved gasses makes it highly explosive.
It defines all pieces of all fragments of rock ejected into the air by an erupting volcano.
Tephra
a hot, chaotic mixture of rock fragments, gas, and ash that travels rapidly (tens of meters per second) away from a volcanic vent or collapsing flow front.
Pyroclastic Flow
Are a deep-seated intrusion of igneous rock, a body that made its way into pre-existing rocks in a melted form (magma) several kilometers underground in the Earth’s crust and then solidified(some mountains and extinct volcanoes).
Plutons
Types of Plutons
*BATHOLITHS- Irregularly shaped masses of coarse-grained igneous rocks that cover at least 100 km2 and take millions of years to form.
*STOCKS- Irregularly shaped plutons that are similar to batholiths but smaller in size.
*LACCOLITHS- Lens shaped plutons with a round top and flat bottom. They are at most, 16 km wide.
*SILLS- Forms when magma intrudes parallel to layers of rock.
*DIKES- Unlike a sill, which is parallel to the rocks it intrudes, a dike is a pluton that cuts across preexisting rocks.
