lesson 4 volcanoes

it is one of the most dangerous natural disasters. It can cause damage to the property and human life.

volcanic eruptions

it sends out ash clouds, lava, and even volcanic bomb

volcanic eruptions

what happens when volcanoes erupt? what are the steps?

1. begins when pressure on the magma chamber builds up, resulting to an explosion.

2. the explosion forces the magma up through the channel and out the volcano’s vents.

3. an explosive eruption of lava, ash, gases, and rocks occurs. The lava flow can cause lahar

• are molten rocks that reach the surface of the earth. = —

• is the flow of volcanic debris = —

• does not always erupt in the same way. = —

• each — is unique, differing in size, style, and composition of erupted material.

state the 9 gases released by a volcanic eruption:

1. lava

2. lahar

3. volcanoes

4. magma composition

• water vapor

• hydrogen sulfide

• sulfur dioxide

• hydrogen chloride

• hydrogen fluoride

• hydrogen

• carbon dioxide nitrogen

• argon

• helium

one key to what makes the eruption unique is the chemical composition of the magma that feeds a volcano, which determines:

1. the eruption style

2. the type of volcanic cone that forms

3. the composition of rocks that are found at the volcano

the words that describe the composition of igneous rocks also describes the magma composition: provide an example for each.

• are low in silica and contains more dark and magnesium and iron-rich — minerals. = —

• are higher in silica and contain lighter-colored minerals. = —

• mafic magmas (olivine and pyroxene)

• felsic magmas (quartz and orthoclase feldspar)

the higher the amount of silica in the magma, the higher its —. this is a liquid's resistance to flow

• felsic magmas

viscosity

types of volcanic eruption and their examples:

• hawaiian - Pu'u O'o Hawaii

• strombolian - Stromboli, Mt. Etna

• vulcanian - Santiaguito (Guatemela)

• plinian - Mt. Pinatubo (Philippines)

in a —, fluid basaltic lava is thrown into the air which lasts for — hours or even days. This phenomenon is called?

• hawaiian eruption

• 4 hours

• fire fountaining

are distinct bursts of fluid lava from the mouth of a magma filled summit conduit

strombolian eruption

eruptions occur every few minutes with the height of the explosion reaching up to hundred of meters

strombolian eruption

it is associated with sall lava lakes and known as the least violent of the explosive eruptions

strombolian eruption

this type of eruption is short, violent, relatively small explosions of viscous magma

vulcanian eruption

it results from the fragmentation and explosion of a plug of lava in a volcanic conduit

vulcanian eruption

it creates powerful explosions (faster than 350 m/s). it is repetitive and can go for days, months or years

vulcanian eruption

it is the largest and most violent among the type of eruption.

plinia eruption

it is caused by the fragmentation of gassy magma and releases enormous amounts of energy

plinian eruption

this eruption can rise up to 50 km. it is extremely destructive and it can obliterate the entire top of a mountain

plinian eruption

— attempt to forecast volcanic eruptions but this has proven to be nearly as difficult as predicting an earthquake. many pieces of evidence can mean that a volcano is about to erupt, but the — and — f the eruption are difficult to pin down

volcanologists, time and magnitude

Earthquakes:

• — shakes the ground, so the number and size of earthquakes increase before an eruption. = —

• a — tthat is about to erupt may produce a sequence of earthquakes. = —

• scientiests use — tthat record the length and strength of each earthquake to try to determine if an eruption is imminent.

• moving magma

• volcano

• seismograph

When magma and gas push the volcano's slope upward, this causes

slope deformation

most ground deformation is subtle and can only be detected by —, which are instruments that measure the angle of the slope of a volcano. = —

(slope deformations)

tiltmeters

• — may sometimes create huge changes in the shape of a volcano.

• ex. — grew a bulge on its north side before its 1980 eruption.

• — mmay also increase rock falls and langslides

(slope deformation)

• ground swelling

• mount st. helens

• rates of emission and type of gas changes in some volcanoes. = —

• important gases include:

• changes in — mmay reflect the movement of the magma up the vent.

gas emissions

• sulfur dioxide (SO2) and carbon dioxide (CO2)

some gases can be monitored using this. — mmonitor temperature readings and deformation

(remote monitoring)

satellite technology

as technology improves, scientists are better able to detect changes in a volcano accurately and safely

remote monitoring

volcanic eruptions can be explosive, sending ash, gas and lava high up into the atmosphere, or the magma can form lava flows, known as —

effusive eruptions

whether an — is explosive or effusive, it largely depends upon the amount of gas in the magma.

eruption