In Mount St. Helens’ case, an oceanic plate called Juan de Fuca slips under the North American plate, creating the Cascadia subduction zone. A continental arc brews adjacent to the subduction zone, where high pressures and hot temperatures force molten rock to the surface. The result is a chain of volcanoes.
What is the tectonic setting of Mt St Helens?
The Cascade Range, where Mount St. Helens resides, is a perfect example of a fundamental concept in geology known as a subduction zone, a place where oceanic crust and continental crust collide. Here, the Juan de Fuca (oceanic) plate dives beneath the North American (continental) Plate.
What type of geologic setting produced the Mt St Helens volcano?
Mount St Helens is located on a destructive plate boundary where two plates are squeezing towards each other. The eruption was caused by the ocean crust (Juan de Fuca plate) subducting under the continental crust (North American plate). The ocean crust was destroyed and formed magma which rose to the surface.
How Mt St Helens was formed?
Mt St Helens is a major stratovolcano in the Cascades Range, all of which have formed as a result of the ongoing subduction of the Juan de Fuca tectonic plate beneath the western coast of North America. Prior to 1980, Mt St Helens was a classical cone-shaped volcano, and a well-visited site on the tourist trail.
What is the tectonic setting of a volcano?
Destructive, or convergent, plate boundaries are where the tectonic plates are moving towards each other. Volcanoes form here in two settings where either oceanic plate descends below another oceanic plate or an oceanic plate descends below a continental plate.
What is the tectonic setting?
Tectonic setting refers to the different tectonic conditions present at a particular location on Earth. It describes whether somewhere is near a tectonic plate boundary or in a more interior position on the plate.
What are the 3 tectonic settings?
As summarized in Chapter 3, magma is formed at three main plate-tectonic settings: divergent boundaries (decompression melting), convergent boundaries (flux melting), and mantle plumes (decompression melting).
What type of volcano is Mount St Helens?
Mount St. Helens, a stratovolcano or composite volcano located in Washington State, USA (46.2º latitude north, 122.2º longitude west,) erupted violently on the Sunday morning of May 18th 1980 at precisely 8:32.
What are 3 tectonic settings where volcanoes commonly occur?
Volcanism occurs at convergent boundaries (subduction zones) and at divergent boundaries (mid-ocean ridges, continental rifts), but not commonly at transform boundaries.
What are the 4 types of tectonic movement?
What are the major plate tectonic boundaries?
- Divergent: extensional; the plates move apart. Spreading ridges, basin-range.
- Convergent: compressional; plates move toward each other. Includes: Subduction zones and mountain building.
- Transform: shearing; plates slide past each other. Strike-slip motion.
What are the 4 types of plate tectonics?
Plate Boundaries and Hotspot Demonstration
- Divergent Plate Boundary. Volcanic eruptions and shallow earthquakes are common where plates rip apart.
- Convergent Plate Boundary.
- Transform Plate Boundary.
- Hotspot.
What tectonic setting causes mountains?
Mountains form where two continental plates collide. Since both plates have a similar thickness and weight, neither one will sink under the other. Instead, they crumple and fold until the rocks are forced up to form a mountain range. As the plates continue to collide, mountains will get taller and taller.
What are the types of tectonic?
There are three kinds of plate tectonic boundaries: divergent, convergent, and transform plate boundaries. This image shows the three main types of plate boundaries: divergent, convergent, and transform. Image courtesy of the U.S. Geological Survey.
In what type of plate boundary did mountains form?
Convergent Plate Boundaries
Convergent Plate Boundaries—Collisional Mountain Ranges.
Which tectonic plates are divergent?
Divergent boundaries
- The East African Rift (Great Rift Valley) in eastern Africa.
- The Mid-Atlantic Ridge system separates the North American Plate and South American Plate in the west from the Eurasian Plate and African Plate in the east.
- The Gakkel Ridge is a slow spreading ridge located in the Arctic Ocean.
What caused Mount St. Helens eruption?
On the morning of May 18, 1980, after weeks of small tremors, a magnitude 5.1 earthquake shook beneath Mount St. Helens and triggered an enormous eruption.
Is Mt St Helens a volcanic arc?
The volcano is part of the Cascade Volcanic Arc, a segment of the Pacific Ring of Fire. The Mount St. Helens major eruption of May 18, 1980 remains the deadliest and most economically destructive volcanic event in U.S. history.
Is Mount St. Helens a cone volcano?
At the event’s end, Mount St. Helens’s volcanic cone had been completely blasted away; in place of its 9,677-foot (2,950-metre) peak was a horseshoe-shaped crater with a rim reaching an elevation of 8,363 feet (2,549 metres).
In what tectonic setting do you find the most explosive volcanoes?
subduction zones
Subduction Zone Volcanism
Most explosive eruptions occur in volcanoes above subduction zones, where one tectonic plate dives beneath the other. Eighty to 120 kilometers below the surface, magma forms when the rocks of the mantle melt just above the subducting plate.
At what 3 tectonic settings do igneous rocks usually form?
Metamorphic Rocks and Plate Boundaries
Metamorphic rocks that form because they are exposed to heat from magma form at the same plate boundaries igneous rocks form: divergent, ocean–ocean convergent, and ocean–continent convergent boundaries. These types of metamorphic rocks can also form at hot spots.
What volcanoes form at convergent boundaries?
Explosive eruptions characterize subduction zone volcanism and create arrays of cone-shaped stratovolcanoes that mark the position of the convergent boundary. Oregon’s Mount Hood is an example of a stratovolcano.