Volcanoes

What is a volcano? A volcano is any place on the planet where some material from the inside of the planet (magma) makes its way through to the planet’s surface.

How are volcanoes formed? 1. At subduction zones (subduction zone volcanism)

How are volcanoes formed? 2. At divergent boundaries (spreading center volcanism)

How are volcanoes formed? 3. At transform boundaries (rarely)

How are volcanoes formed? 4. Over hot spots

What are the properties of magma? 1. Viscosity – the ability of magma to resist flow; high viscosity is associated with explosive eruptions 2. Gas content – the amount of gas dissolved in magma; high gas levels are associated with explosive eruptions

What are the types of volcanic eruptions? 1. Plinian  Magma is highly viscous and has high gas levels  Explosive eruptions produce a towering plume of pyroclastic material and fast moving lava

Plinian eruption

Pyroclastic materials refer to hot ash, pumice, rock fragments, and volcanic gas. Once deposited, the ash, pumice, and rock fragments may deform (flatten) and weld together because of the intense heat and the weight of the overlying material.

What are the types of volcanic eruptions? 2. Hawaiian  Magma is of low viscosity and has low gas levels  Subdued eruptions may produce a fountain of fire or a slow, steady lava flow

Hawaiian eruptions

What are the types of volcanic eruptions? 3. Strombolian  Magma has a fairly high viscosity and low gas levels, taking time to build up a high gas pressure for an eruption to occur  Small, explosive eruptions come in very short bursts, spewing small amounts of lava and ash into the air accompanied by booming sounds. They may have some lava flow.

Strombolian eruption

What are the types of volcanic eruptions? 4. Vulcanian  Magma is highly viscous and has high gas levels  Several short, explosive bursts spew out lava, ash and pyroclastic bombs. No lava flow occurs.

Vulcanian eruption

Volcanic bombs are lava fragments that were ejected while viscous (partially molten) and larger than 64 mm in diameter.

What are the types of volcanic eruptions? 5. Hydrovolcanic  Occur near oceans, saturated clouds or other wet areas  Water turns to steam, producing fine ash from pyroclastic material

Hydrovolcanic eruption

What are the types of volcanic eruptions? 6. Fissure  Occur where plate movement produce fractures in the crust or may also spring up around the base of a volcano  Magma flows up through cracks in the ground as a curtain of slow moving lava

Fissure eruption

What are the parts of a volcano? 1. Summit crater – the mouth of the volcano 2. Magma chamber – a pool of magma beneath a volcano 3. Central vent – leads from the magma chamber to the crater 4. Edifice – the structure surrounding the central vent

Parts of a Volcano Summit crater Edifice Central vent Magma chamber

What are the parts of a volcano? 5. Other structures  Caldera – a large crater-shaped basin produced from the collapse of the volcano edifice  Lava dome – a plug of hardened lava at the summit crater

Parts of a Volcano Caldera

Parts of a Volcano Lava dome

What are the types of volcanoes? 1. Stratovolcano  Also known as composite volcanoes  With a fairly symmetrical edifice with steep slopes and accessory vents  Built up by alternating violent eruptions of pyroclastic material and quiet lava flows

Stratovolcano

What are the types of volcanoes? 2. Scoria cone volcanoes  Also known as cinder cones  Small cones with steep slopes and a wide crater  Usually associated with eruptions of rock and ash and very few lava flows

Scoria cone volcano

What are the types of volcanoes? 3. Shield volcanoes  Wide and short volcanoes with gentle slopes  Usually associated with frequent subdued eruptions of flowing lava

Shield volcano

Volcanoes on Other Planets 1. Venus – covered with hundreds of geologically young volcanoes 2. Mars – has several volcanic features, including the largest volcano in the solar system, Olympus Mons * Mercury and our moon appear to have ceased being volcanically active.

Venus

Mars Olympus Mons

MercuryMoon

Volcanoes on Other Planets 3. Jupiter’s moons  Io – the most volcanically active body in the solar system  Europa – may have ice or silicate volcanic systems

Jupiter’s Moons IoEuropa

Volcanoes on Other Planets 4. Saturn’s moons  Encaladus – may have ice volcanism  Titan – volcanism may account for its dense atmosphere 5. Neptune’s moon  Triton – its dense atmosphere may be due to volcanism

Encaladus Neptune’s moon: Triton Titan Saturn’s moons

Plate Tectonics in the Philippines  Several micro-plates are getting squeezed between two convergent plate margins.  Black triangles = active subduction zones with "teeth" on the over-riding plate, white triangles = inactive subduction, arrows = transform or major strike-slip faults, red triangles = volcanoes active in the last 10,000 years

Volcanoes in the Philippines  With 22 active volcanoes and around 330 potentially active and inactive volcanoes  Mostly cinder (scoria) cones, stratovolcanoes and calderas  Mudflows are common because of heavy rains.  Tsunami are commonly associated with eruptions

Lahar is an Indonesian word for a rapidly flowing mixture of rock debris and water that originates on the slopes of a volcano. Lahars are also referred to as volcanic mudflows or debris flows.

Mayon LOCATION: Albay province Height: 2,460 m asl Type of Volcano: Stratovolcano No. of Recorded Eruptions: 47 since 1616 Latest Eruption: 24 June & 26 July 2001 Most Destructive Eruption: 01 February 1814; 1,200 people perished due to lahars Eruption Types: Strombolian, Vulcanian, Plinian

Kanlaon LOCATION: Negros Island, Central Visayas Height: 2,435 m asl Type of Volcano: Stratovolcano (summit caldera: 15 km² ) No. of Recorded Eruptions: 27 since 1866 Latest Eruption: 10 August 1996 Eruption Types: Hydrovolcanic, Strombolian

Taal LOCATION: Batangas Province Type of Volcano: small cones formed inside a large caldera Highest Point of the Volcano Island: 311 m asl No. of Recorded Eruptions: 33 since 1572 Latest Eruption: 03 September 1977 Destructive Eruptions: several, latest in 1965 as ashfall covered an area of 60 sq. km killed 200 people Eruption Types: Strombolian, Plinian, Hydrovolcanic

Pinatubo LOCATION: at the boundaries of Zambales, Pampanga and Tarlac Height Before the 1991 Eruption: 1,745 m asl Height After the 1991 Eruption: 1,445 m asl Type of Volcano: Stratovolcano with a summit caldera No. of Recorded Eruptions: 2 since 1380 First Observed Major Eruption: 12 June 1991 at 8:51 AM Eruption Type: Plinian

Bulusan LOCATION: Sorsogon Province Height: m above sea level (asl) Type of Volcano: Stratovolcano formed inside a caldera No. of Recorded Eruptions: 18 eruptions since 1852 Latest Eruption: 27 November 1994 Type of Eruptions: Hydrovolcanic, Strombolian

Volcanoes and People Destructive effects 1. People may die or become injured 2. Property may be destroyed 3. People may lose their livelihood (farming) 4. Respiratory disease cases may increase 5. Jet planes may malfunction due to ash in engines

Volcanoes and People Beneficial effects 1. New land masses are formed 2. Soil becomes more fertile 3. Commercially important minerals, rocks and gemstones are produced 4. Locations for spas and resorts and as tourist spots 5. Geothermal energy may be harnessed from volcanic heat

Volcanic delta (Kilauea)

Fertile lands at the base of Mayon

Basalt blocks Pumice scrub Scoria stones

Hot springs in Japan

A Model of a Geothermal Plant

The End