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

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