Volcanic Hazards

Magma

Some parts of the lithosphere go back into the mantle, melting them, and producing molten material.

Lahars

Mudflows composed of volcanic debris and water that can bury communities and infrastructure.

Volcanic ash fall

Accumulations of ash that can collapse roofs, contaminate water supplies, and disrupt transportation.

Pyroclastic Density Currents (PDCs)

Currents of hot gas, ash, and rock that can devastate areas in their path.

Ballistic Projectiles

Fragments of lava (bombs) or rock (blocks) ejected with high kinetic energy during explosive eruptions. These can range from a few centimeters to several meters in diameter and pose a lethal hazard, especially to those near the eruption site.

Volcanic Gases

Emissions that can be toxic and lead to health hazards or environmental damage.

Lava Flows

Molten rock that can destroy structures and vegetation due to its intense heat.

Lahar

• Wet, cement-like mixture of volcanic material and water

• Travels along rivers and water channels and can acquire older volcanic material along the way

• Highly mobile and may manifest in forms of large boulders

• Not exclusively caused by volcanic activity; may also be triggered by intense rainfall. The 1991 Pinatubo eruption resulted in lahars because there was heavy rainfall that also took place during that time.

Tephra

refers to volcanic rock and lava materials that are ejected into the air by explosions or carried upward by eruption column’s hot gases or lava fountains.

Tephra Falls

which skip hugging the slope and go directly to the ground, range in size from less than 2 mm to more than 1 meter in diameter.

Volcanic Ash

which is a type of tephra that is less than 2mm in size, can travel hundreds to thousands of kilometers downwind from a volcano.

Pyroclastic Density Currents (PDCs)

Hot, ground-hugging flows of ash and debris that can travel at speeds of hundreds of meters per second, reaching many tens to hundreds of kilometers

Pyroclastic Flow

dense type of current that moves slower than a pyroclastic surge

Pyroclastic Surge

• diluted type of current that has more mobility and can pass through bodies of water

• its effects involve burns, impact and burial, inhalation of hot ash and gases, as well as lahars and flooding.

Ballistic Projectiles

are a special kind of tephra. These follow a projectile path as these are forced out of the vent at steep angles like a cannon ball, usually landing at 2 to 5 kilometers away from the vent.

Bombs

derived from fresh magma, hence they are molten when

ejected; assume various shapes and attain smoothness upon

impact and cooling.

Blocks

rough and large pieces of broken material from the walls

of the volcanic vent or surrounding rocks; have sharp edges

Volcanic Gases

Aside from molten material and tephra, a variety of gases also get released into the atmosphere during volcanic activity.

Water Vapor H2O

colorless, odorless, and harmless; most abundant;

may manifest as large plumes of white gas (steam)

Carbon Dioxide CO2

colorless and odorless; may cause unconsciousness a nd death in concentrations exceeding 15%

Sulfur Dioxide SO2

colorless with pungent odor; irritant; may create smog

Hydrogen Sulfide H2S

colorless, flammable gas with strong offensive odor

Hydrogen Hallides HF, HBr

toxic acids that quickly dissolve in the atmosphere becoming components of acid rain

Low Silica Magma

low viscosity lava flow; movement at high speeds

High Silica Magma

high viscosity lava flow; movement at low speeds