Everything Else About Volcanoes

Including but not limited to how they erupt, the accompanying hazards, the life cycle, features and

predicting eruptions

How a Volcano Erupts

» Magma collects underneath the volcano in a magma chamber

» Pressure from the earth on the chamber forces magma to rise

» Violence dependent on˃ Pressure˃ Dissolved gases

Volcano Video

» http://www.youtube.com/watch?v=u2V2kAGp91I

Hazards

» Lava flows: eruption of magma at Earth’s surface

» Lava flows vary based on the composition of the magma

Pahoehoe

» pahoehoe: fast moving; low viscosity

» smooth ropy texture when it hardens

» move at a rate of about 1 meter per hour

Aa

» aa: slow moving; higher viscosity

» blocky texture when hardens

» move at rates of a few meters per day

Pyroclastic Activity

» Pyroclastic activity: explosive volcanism where tephra is physically blown into the atmosphere

Tephra

» tephra: any material that is blown out of a volcano (mostly ash)

Ash Fall

» ash fall: huge quantities of rock, glass and gas are blown high into the air

» kills vegetation» contaminate water» structural damage» respiratory irritation

Lateral blast

» lateral blast: explosions of gas and ash from the side of the volcano; destroys part of the mountain

Poisonous Gases

» CO2, carbon monoxide, sulfur dioxide, and hydrogen sulfide

» can cause acid rain; contaminates water supply and vegetation

» lahar: debris flows and mudflows» volcanic debris becomes saturated with water» ex. Mt. Pinatubo, Philippines

Volcano Life Cycle

» An active volcano has erupted recently and is expected to erupt again in the future

» A dormant volcano is not active but may become active in the future

» An extinct volcano is at the end of its life and it is no longer able to erupt

Features

» crater - depression found at the top of a volcano; formed by the explosion of the upper portion of the cone

» hot springs: water is heated by the hot rock and reaches Earth’s surface

» geyser: a hot spring that periodically erupts (RARE!)

» ex. Old Faithful

» caldera: a giant crater that can be more than 12.5 miles in diameter

» formed by rare, very violent eruptions» none have occurred in recorded history (they

are 1000 times more violent than Mt. St. Helens!)

» Yellowstone caldera was formed 600,000 years ago!

Predicting Eruptions

» Monitoring of seismic activity- often the earliest sign

» Thermal monitoring - measuring ground temperatures

» Topographic Monitoring - mountain may tilt and swell before an eruption

» Volcanic Gas Emissions - changes in composition of gases may indicates rising of magma

» Geologic History - geologists map and date rocks around the area