Volcanoes and Eruptions

• Volcanoes are openings in the Earth's crust.
• Magma, gasses and ash erupt onto the surface.
• Volcanoes forms as a result of tectonic activity like subduction, rifting, and hot spots.
• Volcanoes come in different shapes and sizes.
• Some volcanoes are active and erupt frequently.
• Some volcanoes are dormant and extinct.
• When a volcano erupts, events can be spectacular and dangerous.
• Eruptions can produce lava flows, ash clouds and pyroclastic flows.

Parts of a Volcano

• Crater: a bowl-shaped depression at the top of a volcano that forms when the summit collapses after an eruption
• Magma Chamber: a large underground cavity where molten rock (magma) is stored before it erupts
• Conduit: a long, narrow channel that connects the magma chamber to the surface which magma rises and erupts through.
• Fumarole: a vent that emits steam, gas, and other volcanic gases that are found near a volcano's summit.

The Ring of Fire

• Most of the Earth's volcanoes are located in the Ring of Fire.
• The Ring of Fire is a horseshoe-shaped region in the Pacific Ocean.
• The Ring of Fire stretches from South America (Chile) → North America (Alaska) → Japan → The Philippines → New Zealand.
• The Ring of Fire is home to 75% of Earth's volcanoes.
• The Ring of Fire accounts for 90% of the world's earthquakes.
• The Ring of Fire has intense movement of tectonic plates

Volcano Locations

• Volcanoes are located at subduction zones, rift zones and hot spots.

Subduction Zones

• Subduction Zones are where plates collide.
• A subduction zone is an oceanic plate (thinner, denser) forced under a continental plate (thicker, lighter).
• The oceanic plate melts due to high temperatures and pressures, creating magma and thus volcanoes.
• Example: Andes Mountains (Chile, South America) are home to stratovolcanoes like Villarrica.

Rift Zones

• Rift Zones are where plates pull apart
• Rift zones form when tectonic plates move away from each other.
• As plates move away from each other, magma rises and volcanoes form.
• Rift Zones happen along continental rifts and mid-ocean ridges
• Example: The East African Rift which includes Mount Nyiragongo in the Democratic Republic of the Congo.

Hot Spots

• Hot spots are volcanoes in the middle of plates.
• A hot spot is a fixed area deep in the Earth where hot magma rises through the crust, creating volcanoes.
• Hot spots remain in the same place, but as tectonic plates move over them, they form chains of volcanoes over time.
• Example: The Hawaiian Islands were formed by a hot spot in the middle of the Pacific Plate.

Mid-Ocean Ridges

• Mid-Ocean Ridges are underwater volcanoes.
• The ocean floor is constantly spreading at divergent boundaries.
• When plates separate, magma rises to fill in the gap, creating new oceanic crust and hence volcanoes.
• Over millions of years, the process can build underwater mountain chains.
• Example: The Mid-Atlantic Ridge is an underwater volcanic mountain range in the Atlantic Ocean.
• The North American Plate and Eurasian Plate are moving apart here which widens the Atlantic Ocean.

Plate Boundaries

• Different types of volcanic activity occurs at the edges of tectonic plates.
• Plates collide, pull apart, or slide past each other, which are known as plate boundaries.

Volcanic Activity

• Volcanoes are classified as active, dormant, or extinct.

Active Volcanoes

• An active volcano is currently erupting, has erupted recently, or shows signs of erupting in the near future.
• Direct connection to a magma source which moves beneath the surface.
• Active volcanoes release steam, ash and gases(like sulfur dioxide), or lava, even when they are not fully erupting.
• Examples: Mount Etna (Italy), Kilauea (Hawaii, USA), and Taal Volcano (Philippines)
• Signs for volcano will erupt soon:
  • Increased earthquakes
  • Changes in emission of gases (sulfur dioxide)
  • Bulging or swelling due to rising magma.
  • Sudden temperature changes in nearby hot springs or crater lakes

Dormant Volcanoes

• A volcano that has not erupted for a long time (hundreds or thousands of years).
• Dormant volcanoes have the potential to erupt again because they still have an inactive magma source
• Scientists monitor dormant volcanoes because they can suddenly become active again.
• Examples: Mount Rainier (USA), Mount Fuji (Japan), Mount Pinatubo (Philippines)
• Why Dormant Volcanoes Can Be Dangerous:
  • People often build near them and they can erupt with short notice.
  • Mount Vesuvius (Italy) was dormant before its eruption in 79 AD which buried Pompeii and Herculaneum.

Extinct Volcanoes

• Has not erupted for thousands or millions of years.
• No longer connected to a magma source.
• Magma chamber has cooled and solidified.
• Erodes over time and losess original shape.
• Examples: Mount Kilimanjaro (Tanzania), Edinburgh Castle Rock (Scotland), Shiprock (USA)
• Volcanoes become extinct because of:
  • Tectonic plates moving where magma supply gets cut off from hot spots like Hawaii.
  • Magma chambers cooling.
  • Erosion and weathering by wind, rain and glaciers which leaves behind only volcano remnants.

Types of Volcanoes

• Shield Volcanoes
• Stratovolcanoes
• Cinder Cones

Shield Volcanoes

• These volcanoes have a broad, gently sloping cone shape.
• Formed by numerous lava flows that spread from a central vent.
• Shield volcanoes typically have non-explosive eruptions.
• Tend to produce thin, runny lava that flows for long distances.
• Example: Mauna Loa and Kilauea in Hawaii.

Stratovolcanoes

• Tall, steep-sided volcanoes with a classic, cone-shaped appearance.
• Formed by alternating layers of lava, ash, and other volcanic debris
• Stratovolcanoes have explosive or non-explosive eruptions.
• Well-known for powerful explosions and pyroclastic flows.
• Example: Mount Fuji in Japan and and Mount St. Helens in the U.S.

Cinder Cones

• Small, steep-sided volcanoes made of loose, pyroclastic material.
• Includes ash, cinders, and volcanic bombs.
• Formed by explosive eruptions from a single vent, which piles material around the vent.
• Examples: Mauna Kea in Hawaii and Mount Etna in Italy

Types of Volcanic Eruption

• Volcanic eruptions occur when magma rises to the surface and erupts through a vent in Earth’s crust.
• Various types of volcanic eruptions classify based on the type of magma, gas amounts, and style of eruption.
• Vulcanian Eruptions
• Plinian Eruptions
• Pelean Eruptions
• Strombolian Eruptions
• Hawaiian Eruptions
• Icelandic Eruptions
• Surtseyan Eruptions

Vulcanian Eruptions

• More stronger than Hawaiian and Strombolian eruptions.
• Ejects large amounts of ash, gas, and rock fragments.
• Eruption column can reach kilometers.
• Ash can travel long distances.

Plinian Eruptions

• Most explosive type of volcanic eruption.
• Erupts large amounts of ash, gas, and pumice.
• Air forms a mushroom-shaped cloud.
• Cloud reaches several tens of kilometers into the atmosphere.

Pelean Eruptions

• Volcanic vent becomes blocked by viscous magma.
• Build-up of pressure.
• Violent explosion occurs and the pyroclastic flow moves at extremely high speeds, reaching hundreds of kilometers per hour.

Strombolian Eruptions

• Frequent, small explosions that eject cinders, ash, and blobs of molten lava.
• Buildup of gas bubbles in the magma that burst.

Hawaiian Eruptions

• Effusive eruption of basaltic lava.
• Flows out of the volcano and spreads over a large area - forming shield volcanoes.
• Tend to be non-explosive.
• Flows steadily and slowly.

Icelandic Eruptions

• Typically non-explosive and relatively gentle
• Lava flows out of fissures or vents in the Earth's crust.
• The lava flows can flow over large distances, creating vast lava fields and shield volcanoes.

Surtseyan Eruptions

• Interaction between magma and water.
• Leads to explosive eruptions with steam, ash, and rock fragments.
• Creates a rapidly expanding seam-filled cavity.

Effects of Volcanic Eruptions

• Property Damage
• Water Pollution
• Air Pollution
• Health Hazards
• Soil Fertility
• Geothermal Energy
• New Landforms
• Tourism Spot

Property Damage

• Lava flows, pyroclastic flows, or lahars (mudflows) can cause significant damage.
• Can destroy buildings, infrastructure, and agricultural land.

Water Pollution

• Ash and materials are released into bodies of water.
• The water can kill fish and other aquatic life.
• Water contaminates drinking water supplies.

Air Pollution

• Eruptions release sulfur dioxide and carbon dioxide.
• Gases react with compounds in the air and lead to the formation of acid rain and smog.

Health Hazards

• Ash and other particles are harmful when inhaled.
• Can cause respiratory problems and aggravate existing health conditions.

Soil Fertility

• Volcanic ask is rich in minerals and provides rich-soil for plant growth.
• Volcanic soils of the Hawaiian Islands help produce highly productive agricultural land.

Geothermal Energy

• Volcanic activity can produce geothermal energy and harnesses electricity.
• It provides a clean and sustainable source of energy in areas with with volcanic activity.

New Landforms

• Provides new habitats for plants and animals.
• Supports new ecosystems.

Tourism Spots

• Volcanoes and their features such as hot springs, geysers, and lava fields are popular tourist attractions.
• Economic benefits to the local communities.

Explore volcano characteristics, eruption types like Pelean and Hawaiian, and geological features such as calderas. Learn about magma sources, volcanic gases and the Ring of Fire.