Volcanoes

Chapter 3 book F page 82

Vocab for section 1

• Volcano• Magma• Lava• Ring of fire• Hot spot

Section 1 volcanoes and plate tectonics page 82 book F

• We all know what volcanoes look like but what is a volcano?– Volcano : is a week spot in the crust where molten

material or magma comes to the surface from the mantle. • what is magma? Magma is a material , consisting of a

mixture of rock forming elements, gases and water from the mantle. – This just leavs lava, is lava different than magma? What is lava

» Lava :it’s magma that has reached the surface.

Volcanoes and plate boundaries.

• Today there are around 600 active volcanoes on land and many more under water. Volcanoes occur in belts, that extend across continents and oceans. The most famous belt is know as the ring of fire. – Ring of fire: formed by the many volcanoes that

rim the Pacific Ocean. – Volcanic belts always form along one of the Earths

plate boundaries.

Volcanoes and the plate boundaries continued

• Plate boundaries are places where there is a lot of turmoil, and unstable conditions. This creates a perfect environment for volcanoes. With the pulling apart or pushing together of plates this creates weak spots for magma to reach the surface. These turn into volcanoes.

Hot spot volcanoes

• Hot spot: is a place where magma from deep within the mantle melts through the crust above it. – A volcano will form above a hot spot when magma

erupts through the crust and reaches the surface. • These are the volcanoes that form away from the plate

boundaries, – Can you name the three most famous hot spots.

» Yellow stone» Hawaiian Island» Galapagos Island

Section 2 properties of magmapage 87 book F vocab

• Compound• Viscosity• Silica• Pahoehoe• aa

Physical and chemical properties

• Like everything else lava is made up of elements and compounds. Depending on what they are made of will determine the lavas physical and chemical properties. – This can effect how hard the rock is its color,

density , reactivity with it’s environment.

Viscosity, what is it?

• Viscosity: Is the resistance of a liquid to flowing.

• Because liquids differ in viscosity some liquids flow more easily than other’s.– the greater the viscosity the greater it flows, the

less the viscosity the more easy it flows.• Examples of low viscosity : water, rubbing alcohol,

vinegar. • Examples of high viscosity : honey , molasses, and corn

srup.

Viscosity and magma

• Does all of the lava have the same viscosity?– No but why?– It’s because of the diffrent elements that the

magma is made of when it comes to the surface. The viscosity depends on the amount of silica in the magma and the temperature.• The amount of silica also determines what type of rock

the lava will cool into, – High silica content = rhyolite, which is that same as granite– Low silica content = Basalt, what the seafloor is made of.

Pahoehoe & aa

• Pahoehoe : a hot fast moving type of lava that hardens to form smooth ropelike coils.

• aa: a slow moving type of lava that hardens to form rough chunks; cooler than pahoehoe.

Volcanic Eruptionsvocab for section 3 book F pg 91

• Magma chamber• Vent • Lava flow• Pyroclastic flow• Dormant • Extinct • pipe

Volcanic Eruption

• What effects a volcanic eruption?

• What causes the eruption

• What effects how long the eruption last’s

Inside a volcano

• All volcanoes have a pocket of magma beneath the surface and one or more cracks through which the magma forces it’s way to the surface. Beneath a volcano magma collects in a pocket called a magma chamber.– Magma chamber: the pocket beneath the volcano

where magma collects. • It get to the surface through the pipe.– Pipe: a long tube in the ground that connect the

magma chamber to the surface

Eruption continued

• Often there is a main vent that allow the magma and gas to escape , – this allows the lava to get out

• Lava flow: is an area covered by lava as it pours out of the vent.

• Crater : is a bowl shaped area that may format the top of the volcano around the central vent.

• Think of a soda when you think of a volcanic eruption. The closer to the surface these gases get to the bigger and more violent the eruption.

The different types of eruptions

• Geologist classify volcanic eruptions a quiet or explosive, the physical properties of its magma determines the type of eruption, the type also depends on its silica and viscosity.– Quiet eruption: low silica, and low viscosity allows

the gas bubbles out gently and are able to escape easily causing a quiet eruption.• Example of this type: Hawaii Island.

Different types of eruptions continued

• Explosive eruption: high silica, high viscosity , thick and stick type magma where the gas bubbles are trapped and build up to the point where they explode. The gas and water push the magma out with an incredible force. – Pyroclastic flow: occurs when an explosive

eruption hurls out a mixture of hot gases, ash, cinders, and bombs.

Stages of volcanic activity

• Active: is a volcano that is currently expelling lava.

• Dormant: a volcano that geologist expect to become active in the future.

• Extinct: is a dead volcano unlikely ever to erupt again.

Geothermal activity

• Hot spring, geysers, and geothermal energy are all signs of magma near the surface of the Earth. – Hot spring: forms when ground water is heated by

nearby body of magma. – Geyser: is a foutain of steam and water the erupts

from the ground.

Volcano quiz

1. What is viscosity?2. Give examples of something with high

viscosity? 3. Give and example of something with low

viscosity?4. What is the major element that influences

lava?5. What is a hot spot?