Volcanoes, Geomorphology and Earth's Surface

• Volcanoes are fractures where lava, tephra, and steam erupt onto the Earth's surface.

Geomorphology

• Geomorphology studies the relief features of Earth's crust.
• Diastrophism, erosion, and volcanism are the three primary geologic forces that continually alter the planet's surface.

Diastrophism

• Diastrophism refers to the vertical and horizontal movement of the crust that typically produces mountains.

Erosion

• Erosion is the physical removal of rock or wearing down of landmasses by geomorphic agents.
• Weathering is the decomposition of rocks and minerals exposed to Earth's surface.

Volcanism

• Volcanism involves surface discharge of magma or hot water and steams, including volcanoes, geysers, fumaroles, and hot springs.
• Volcanoes were widely distributed in all continents in early times.

Cone

• Cones are triangle-shaped hills formed from the accumulation of volcanic eruption material around a volcanic vent (opening) in Earth's crust.

Vent

• A vent is the opening through which an eruption occurs and supplies magma from the underlying source to the top of the volcano.

Magma Chamber

• A magma chamber is a large underground pool of liquid rock beneath the Earth's crust.

Crater

• A crater is a basin-like depression over a vent at the summit of the cone.

Caldera

• A caldera is a volcanic depression much larger than the original crater.

Lava

• Lava is the rock or magma expelled from a volcano during an eruption.

Flank

• The flank is the side of a volcano.

Summit

• The summit is highest point/apex of volcano.

Throat

• The throat is the entrance of a volcano.

Ash Cloud

• An ash cloud, expelled in the atmosphere, contains pulverized rock during an eruption.

Volcanic Bombs

• Volcanic bombs are chunks of lava blasted into the air that solidify before reaching the ground.

Pyroclastic Flow

• A pyroclastic flow is a fast-moving current of hot gases, magma, and rocks travelling downhill from a volcano.

Lahar

• Lahars, also called mudflows, are flowing mixtures of volcanic debris and water that can be classified as being hot or cold.

Cinder Cones (Scoria cones)

• Cinder cones are the simplest type of volcano, with a conical hill formed above a vent composed mostly of basalt.
• They are much smaller than other volcanoes and are considered temporary landforms on a geologic timescale.

Composite Volcanoes (Stratovolcano)

• Composite volcanoes consist of alternating layers of pyroclastic materials with high silica content and solidified lava flows.
• The conduit system consists of a central and clustered group of vents.
• Their size and composition are larger than cinder cones, primarily composed of andesite, tephra, and volcanic ash.
• The slopes of composite volcanoes are symmetrical, with intermediate steepness compared to cinder cones.

Shield Volcano

• A shield volcano is a broad, gently sloping landform built by many layers of very slow-moving lava flows.
• Eruptions of shield volcanoes are relatively non-violent.

Volcanic Domes

• Volcanic domes are round, steep-sided mounds formed of masses of lava primarily composed of dacite or rhyolite.
• The lava coming from a volcanic dome is too viscous to flow from the vent.
• Domes are associated with non-explosive lava eruptions.

Supervolcanoes

• Supervolcanoes produce the largest eruptions on Earth.
• Supervolcanoes need to have recorded an eruption with a magnitude of 8 on the Volcano Explosivity Index (VEI).

Submarine Volcanoes

• Submarine volcanoes are created when magma erupts in the underwater fissures of Earth.
• Submarine volcanoes eject basaltic magma.
• The high and confined pressures at the seafloor prevent them from growing in size.
• During an eruption of these volcanoes, steam and gases fail to be released into the atmosphere or even make any disturbance at the surface of the ocean.

Volcanic eruption

• Volcanic activity varies from the release of gases and non-explosive lava emission to extremely violent explosive bursts.

Classification of volcanic eruptions

• There are two types of eruptions based on activity: explosive and effusive.

Explosive Eruption

• Explosive eruptions get characterized by gas-driven explosion that propels magma and tephra.

Effusive Eruption

• Effusive Eruptions are are outpouring of lava without significant explosive eruption.

Meta types of eruptions

• Geologists classify volcanic eruptions according to three meta-types of eruptions: magmatic, phreatomagmatic, and phreatic.

Magmatic

• Magmatic eruptions are the most well-observed and produce juvenile clasts during explosive decompression of gas within magma that propels it forward.

Phreatomagmatic Eruption

• Phreatomagmatic eruptions get characterized by explosive water-magma interaction through which large amounts of steam and magmatic gases are released.

Phreatic Eruption

• Phreatic eruptions occur when rising magma contacts ground or surface water.
• These eruptions result in water explosion, steam, ash, rock, and gas emission.

Volcanoes are fractures in the Earth's surface where lava, tephra and steam erupt. Geomorphology studies the relief features of the Earth. Diastrophism, erosion, and volcanism are the three primary geologic forces that continually alter the planet's surface.