POWER-UP 2/9 • Have your textbook on your desk and with it open to show your name. • Be ready for more note-taking today.
CHAPTER 9 • Volcano – are places on the surface of the earth that magma and volcanic gas are released • Explosive eruption – An eruption that is mostly pyroclastic material and debris • Non-explosive eruption – an eruption that is mostly lava with almost no pyroclastic material
Types of lava • Aa (ah-ah) – flows quickly and creates a brittle crust which is torn into jagged edges as more lava pushes out past it.
Pahoehoe (pah-hoy-hoy)- very runny, flows like dripping wax. Hardens like melted glass
Pillow lava – forms underwater. Looks like large puffs of pillow (not soft, still a rock)
Blocky lava – stiff lava that flows slowly then breaks into jumbles of brick like pieces.
PYROCLASTIC MATERIALS • Volcanic ash – exploded pieces of hardened magma that are now similar to the size of flour
Lapilli (la-pill-ee) – little stones that are magma drops which hardened while in the air
Volcanic bomb – large blobs of magma that hardened into rock while flying in the air. Between the size of a football to a big beach ball (do not explode)
Volcanic Blocks – largest piece of pyroclastic material. Huge amounts of magma that harden in the air.
PYROCLASTIC FLOW • Most destructive part of an explosive eruption. Pyroclastic flow is when those four types of pyroclastic material (blocks, bombs, lapilli, and ash) travel down the mountainside at over 100mph at temperatures that exceed 1400 degrees. Over a HUGE distance.
VOLCANOES AND WEATHER • Large explosive eruptions can lower global temperature because the ash blocks out a lot of sunlight • After many explosive volcanoes there are flash floods
TYPES OF VOLCANOES • Shield volcano – built by layers of runny lava building up. HUGE mounds that grow off the ocean floor and create islands. Gentle sloping sides. Non-explosive eruptions.
Cinder Cone volcano – Made from layers of pyroclastic material. Very steep sides. Caused by moderate sized explosive eruptions. Grow quickly, are active for a short time, erode quickly.
Composite Volcano – Made of alternating layers of pyroclastic material and lava. Look like mountains. Get steeper towards the top. Made from explosive eruptions followed by non explosive eruptions.
MAGMA • More pressure = more solid • More temperature = more liquid SO • Decrease in pressure means eruption • Increase in temperature means eruption
What could cause that? • What are some things that could cause pressure to decrease inside the earth?
WHERE VOLCANOES ARE • The ring of fire – all around the pacific ocean where there are convergent boundaries
Hot Spots – a place on the crust above an especially hot part of the mantle • Often hotspots create island chains like Hawai’i
Divergent boundaries – midocean ridges are like long volcanoes that create all that new oceanic lithosphere • Convergent boundaries – Subduction zones pull water underneath with them and that water makes the magma more explosive. Also the earthquakes make cracks that are easier for magma to get through
PREDICTING VOLCANOES • An increase in seismic activity (earthquakes) means that a volcano is more likely to happen soon • Because there is less pressure after the earth cracks so the magma is more liquid and likely to get out • An increase in volcanic gases means a volcano is more likely • An increase in temperature at the central vent means a volcano is more likely