Tenaga Endogen Part 2 : VULKANISME

Volcanism

Volcanism is the movement of magma from within Earth. Magma is hot molten rock containing minerals and gases. It may remain underground or reach the surface, producing different landforms, eruptions, and volcanic materials.

Magma movement and underground features

Magma intrusion occurs when magma enters cracks or spaces in the lithosphere but does not reach the surface. The video describes several forms:

• Laccolith: Magma pushes up the rock layers above it, forming a lens-like dome with a flatter base.
• Dyke (dike): A sheet of magma that cuts across the surrounding rock layers.
• Batholith: A large intrusive body of magma near a magma chamber.
• Sill: A relatively thin sheet of magma that lies between rock layers.
• Diatreme: A pipe-like intrusion connecting a magma chamber toward the surface.

When intruded magma cools underground, it forms intrusive igneous rock.

Magma extrusion occurs when magma rises to and emerges at Earth’s surface, commonly during a volcanic eruption.

Ways eruptions are classified

By strength and style

• Explosive eruptions involve powerful blasts that propel volcanic material into the air.
• Effusive eruptions release flowing lava, often through openings or cracks.

By where magma emerges

• Fissure (linear) eruptions emerge along extended cracks and can form lines of volcanoes.
• Areal eruptions occur across several points where magma approaches the surface.
• Central eruptions emerge through a central vent and can build a volcanic cone.

Eruption types

The subtitles name seven eruption styles. Some names may be garbled by automatic transcription.

• St. Vincent type: Described as having a relatively moderate eruption scale but high intensity, with thick lava and stratovolcano formation.
• Merapi type: Thick lava blocks the crater, pressure builds behind it, and an eruption can generate a hot cloud called wedhus gembel in the video.
• Hawaiian type: Relatively small-scale eruptions with fluid lava, associated with shield volcanoes.
• Strombolian type: Repeated bursts at fairly regular intervals release gas and solid volcanic material. Mount Raung is given as an example.
• Vulcanian type: Releases both solid fragments and lava. Mount Semeru is cited as an example.
• Pelean type: A blockage near the summit increases pressure until it fails.
• Plinian type: A highly destructive eruption that can remove or collapse the summit and form a caldera. The video mentions a high eruption column and the 1883 Krakatoa eruption.

Main volcano shapes

• Maar volcano: Formed by an explosive eruption, often described as occurring once when the magma chamber is shallow. It can leave a large crater or caldera. Examples named include Dieng, Gamalama, and Tambora.
• Cone or composite volcano: Built through alternating effusive and explosive eruptions, creating layers of different volcanic materials. The video names Kerinci, Pangrango, and Merbabu.
• Shield volcano: Formed by fluid lava spreading widely, producing broad, gently sloping sides. Mauna Loa and Mauna Kea in Hawaii are examples.

Materials released by volcanoes

Solid material (ejecta or tephra)

The video distinguishes fragments from surrounding crater rocks from material originating in magma. By size, it lists large bombs, smaller rock fragments, gravel-sized material, sand, and ash.

Liquid material

• Lava: Magma that reaches the surface.
• Hot lava or mud: Described as a mixture of magma and water, sometimes involving crater-lake water.
• Cold lava (lahar): Volcanic deposits remobilized into mud by rain. The video notes that this can happen long after an eruption.

Gases (exhalations)

These include sulfur gases (solfataras), water vapor (fumaroles), and carbon dioxide.

Warning signs and after-effects

The video lists these possible signs of impending volcanic activity:

• Sudden warming around the volcano.
• Drying water sources.
• Earthquakes and increasingly loud rumbling.
• Trees losing leaves or dying.
• Wild animals fleeing.
• Stronger gas or vapor emissions.

People living near an active volcano are advised to prepare to evacuate to a safer place if these signs appear.

After an eruption, the video mentions gas emissions, hot springs, mineral or health-related springs (the term in the subtitles is unclear), and geysers, which periodically eject hot water. Iceland and New Zealand are given as examples of places with geysers.

Speakers and sources

• Narrator/presenter: Rodhia Izzati, as identified by the channel context.
• No other speakers or interviewees are identifiable in the subtitles.