VOLCANOES AND IGNEOUS ROCKS

Volcanoes: (write down the orange stuff)

“volcano” comes from the Roman word “Vulcan”, who was the God of Fire

Volcano has several meanings: hole in the ground and lava mountain

Volcanoes shape the earth

Blow tops off mountains and topple forests

Bury cities Change the weather Create islands Create lakes

Crater Lake, OR

Active?

Active volcanoes are currently erupting or have erupted during written history

Dormant volcanoes are sleeping – they are expected to erupt sometime in the future

Extinct volcanoes are not expected to erupt ever again

Types of Volcanoes

Cinder cones spew dusty ash that can pile up. Paricutin produced a cinder cone in a Mexican farmer’s cornfield that piled up ash 300 meters high (as tall as a 60-story building) in one year.

Types of Volcanoes

Shield volcanoes have gently sloping sides because lava just oozes out the top. Mauna Kea is a shield volcano in Hawaii. It is also the tallest mountain on earth (if measured from the mantle.)

Types of Volcanoes

Stratovolcanoes are kinda like cinder cones and shields combined. They have steep sides and layers of lava and ash (layers = strata.) Mount Saint Helens in Washington is a stratovolcano.

Why?

Volcanoes exist because the crust is in constant motion.

When plates separate, or go underneath each other, or move over a “hot-spot” in the magma, a volcano is created.

Under the Hawaiian islands is a hot-spot.

Watery Volcanoes

Geysers are kinda like volcanoes because they transfer heat and kinetic energy from the mantle to the surface.

Instead of lava, though, they spurt hot water.

History Makers

Deadly Volcano Fart. In 1986 a cloud of CO2 killed 1700 people and cows in Cameroon, Africa. Lake Nyos fills a volcanic crater, and the CO2

leaked from the volcano into the lake, then suddenly into the air. (for some unknown reason)

History Makers

Long and Slow. Mount Kilauea has been erupting continuously since 1983. Lava pours into the ocean where it hardens into rock, making the island of Hawaii larger every day.

History Makers

Time Capsule. In AD 79, Mount Vesuvius erupted and covered the Roman city of Pompeii. The ash “froze” people so quickly that some were discovered (years later) still standing up and a bakery still had bread in the oven!

History Makers

Climate Change? Mount Pinatubo in the Philippines erupted in 1991. The ash from the volcano was so thick that people had to drive with their car headlights on during the day, and clouds from the volcano lowered temperatures around the world.

Fiery Rocks

As lava cools, it hardens into different kinds of igneous rocks.

Igneous = ignite = fire

Different mixes of minerals and different speeds of cooling make the different forms of igneous rocks.

Slow, Underground Cooling

Granite Slow cooling produces large crystals and

a coarse texture. Very durable

Quick, Above-ground Cooling Basalt Quick cooling produces small crystals

that can usually only be distinguished in microscope

Sometimes cooled underwater

Very Fast, Above-ground Cooling Obsidian Crystals do not have time to form

because the lava cools so quickly – in minutes or days. Smooth, glassy texture.

Frothy lava

Pumice or Scoria Magma is filled with gasses that are

trapped as the minerals cool. Very lightweight and full of holes.