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Extrusive volcanic features diagram
Volcanic Landforms: Extrusive Igneous
Volcanic processes are constantly changing the Earth. Eruptions can create new islands.
build and destroy mountains, and alter landscapes.
Active, dormant, and ancient remnants of eruptions are all contained within our National Parks.
Shield volcanoes- Volcanoes ranging in size from small to truly massive, created by steady, non-violent outpouring of lava.
Mauna Loa and Mauna Kea in Hawaii are shield volcanoes rising nearly 9 km (5.6 mi) from the seafloor.
. Mount St. Helens and Mount Rainier are stratovolcanoes.
Cinder cones- Short, steep volcanoes associated with limited eruptive events.
Sunset Crater Volcano and Capulin Volcano are cinder cones.
Lava Domes-Lava domes form where thick (viscous) magma erupts to the surface forming a steep dome-shaped landform.
Lava domes can form within a crater of large composite volcano.
–maar-diatreme volcanoes are formed.
by the explosive result of subsurface magma coming into contact with shallow ground water.
The maar is the crater landform produced by explosive eruption(s) and the diatreme is the below surface rock filled volcanic pipe or conduit.
Conical Vent and Fissure Vent
A fissure vent (volcanic fissure) is a narrow, linear volcanic vent through which lava erupts, usually without any explosive activity.
The vent is often a few meters wide and may be many kilometres long.
Fissure vents are common in basaltic volcanism (shield type volcanoes).
A conical vent is a narrow cylindrical vent through which magma flows out violently.
Conical vents are common in andesitic volcanism (composite or stratovolcano).
The central portion of the mid-ocean ridges experiences frequent eruptions.
Composite Type Volcanic Landforms
They are conical or central type volcanic landforms.
Along with andesitic lava, large quantities of pyroclastic material and ashes find their way to the surface.
Andesitic lava along with pyroclastic material accumulates in the vicinity of the vent openings leading to the formation of layers,
and this makes the mounts appear as a composite volcano or a stratovolcano (divided into layers).
The highest and most common volcanoes have composite cones.
Mount Stromboli (the Lighthouse of the Mediterranean).
Mount Vesuvius, Mount Fuji are examples.
Shield Type Volcanic Landforms
The Hawaiian volcanoes are the most familiar examples.
These volcanoes are mostly made up of basaltic lava (very fluid).
These volcanoes are not steep.
They become explosive if somehow water gets into the vent;
Example: Hawaiian volcanoes Mauna Loa (active shield volcano) and Mauna Kea (dormant shield volcano).
Fissure Type Flood Basalt Landforms (Lava Plateaus)
Sometimes, a very thin magma escapes through cracks and fissures in the earth’s surface .
and flows after intervals for a long time, spreading over a vast area.
Example: Siberian Traps, Deccan Traps, Snake Basin, Icelandic Shield, Canadian Shield.
A crater is an inverted cone-shaped vent through which the magma flows out.
In some volcanoes, the magma chamber below the surface may be emptied after volcanic eruptions.
The volcanic material above the chamber collapses into the empty magma chamber.
and the collapsed surface appears like a large cauldron-like hollow (tub shaped) called the caldera.
A lava dome (volcanic dome) is a mound-shaped protrusion.
(a structure that extends outside the surface) resulting from the slow extrusion.
(coming out) of viscous lava from a volcano.
In Lava domes, viscous magma piles up around the vent.
Pseudo volcanic features
Salt extrusions may take the form of salt hills which exhibit volcanic crater like features.
Salt structures are impermeable and can lead to the formation of a stratigraphic trap.
(an impermeable layer capable of retaining hydrocarbons.
Intrusive and extrusive volcanic landforms
Volcanic Landforms and Geothermal Activity
As you know, magma is molten rock found beneath the Earth’s surface.
Sometimes, it appears at the surface of the Earth as lava after moving through a volcano.
The rocks that solidify beneath the ground are called intrusive or plutonic rocks.
Extrusive rocks are sometimes small rocks that you can hold in your hand.
Intrusive rocks do not always remain hidden below the surface.
Hot springs and geysers are some more examples of surface features related to igneous rock.
- List and describe landforms created by lava.
- Explain how magma creates different landforms.
- Describe the processes that create hot springs and geysers.
Landforms from Lava
The most obvious landforms created by lava are volcanoes.
volcanoes come in many forms, most commonly as cinder cones, stratovolcanoes,
and shield volcanoes.
Oceans and continents exemplify the highest-order landforms.
Landforms may be extracted from a digital elevation model using some automated techniques where the data has been gathered by modern satellites.
and stereoscopic aerial surveillance cameras. Until recently.
compiling the data found in such data sets required time consuming,
and expensive techniques involving many man-hours.
The most detailed DEMs available are measured directly using LIDAR techniques.
What is the difference between intrusive and extrusive volcanic landforms?
Explain how volcanic landforms are classified.
Briefly explain all intrusive landforms with examples.
Volcanic landforms are divided into extrusive and intrusive landforms based on weather magma cools within the crust .
or above the crust.
The intrusive activity of volcanoes gives rise to various forms.
They appear on the surface only after the denudation processes remove the overlying materials .
and may be exposed on the surface after erosion.
Example: Wicklow mountains of Ireland; the uplands of Brittany, France.
These are large dome-shaped intrusive bodies connected by a pipe-like conduit from below.
Example: The laccoliths of Henry mountains in Utah, USA.
Example: The Bushveld lopolith of Transvaal, South Africa.
These are called the Phacoliths.
Example: Corndon hill in Shropshire, England.
These are solidified horizontal lava layers inside the earth.
Example: Great whin sill of North East England
Volcanic activities have a profound influence on the earth’s landforms.
Solid, liquid or gaseous materials may find their way to the surface from some deep-seated reservoir beneath.
What is intrusive and extrusive volcanism?
What are the three types of volcanic landforms?
- Mostly, the low viscosity basaltic lava which is high in fluidity form Shield volcanoes. It leads to the formation of the extrusive igneous rocks.
- Shield volcanoes are the largest volcanoes in the world.
- They extend to greater heights and distances. Examples of Shield volcanic landforms include Mauna Loa volcanoes of Hawaii.