BellringerWhat happens to the oldest islands in a volcanic

island chain created by a mantle hot spot?

Properties of Magma

Notes

Physical and Chemical Properties•Like other substances, magma is made up of

elements and compounds, and has a certain set of properties, or traits. Properties can be physical or chemical.

•An element is a substance that cannot be broken down into other substances. Carbon, Oxygen, Argon, Gold, Tin, Lead, etc.

•A compound is a substance made of two or more elements that have been chemically combined. Water, Carbon Dioxide, Table Salt, Sulfuric Acid, etc.

Elements Compounds

C

O

H

Physical and Chemical Properties•Physical properties are traits that

can be observed without changing what a substance is made of. Examples of physical properties are hardness, color, density, melting point, boiling point, and magnetism.

•Water, under normal pressure, will always have a melting point of 0°C and a boiling point of 100°C.

Physical and Chemical Properties• Chemical properties are traits that can be

observed only by changing what a substance is made of. Examples of chemical properties is a substances ability to burn and its ability to combine, or react, to another substance.

• You can often tell if a substance has reacted to another substance if it changes color, produces a gas, or forms a new, solid substance (precipitate).

• Iron’s reaction with oxygen to produce rust is an example of a chemical property.

What is Viscosity?

•Viscosity is a physical property of liquids. How well a liquid flows depends on its viscosity.

•A liquid with a high viscosity is thick. It flows very slowly. Honey and syrup have high viscosities.

•A liquid with low viscosity is thin. It flows very quickly. Water and Kool-Aid® have low viscosities.

•The greater the friction between the fluid’s particles, the higher the viscosity.

Video - Three different viscosities

http://upload.wikimedia.org/wikipedia/commons/b/b7/Viscosity.gif

Viscosity of Magma

•Silica is a common substance in Earth’s crust. Magma contains silica. Magma that contains more silica has higher viscosity.

•High-silica magma produces high-viscosity lava. This lava flows slowly.

•High-silica magma cools to form light-colored, felsic igneous rocks such as granite, pegmatite, and rhyolite.

Rhyolite Granite

Pegmatite

Viscosity of Magma

•Low-silica magma produces low-viscosity lava. This lava flows quickly.

•Low-silica magma cools to form dark-colored, mafic igneous rocks such as basalt and gabbro.

Basalt Gabbro

Viscosity of Magma•Hotter magma has lower viscosity than

cooler magma.

•Very hot magma produces lava called Pāhoehoe. Pāhoehoe has low viscosity. It flows quickly. It hardens into a rippled surface.

•Cooler magma produces lava called ʻaʻā. ʻAʻā has high viscosity. It flows slowly. It hardens into rough chunks.

Pāhoehoe ʻAʻā

Lava Type

Temperature ViscositySilica

ContentColor

RockExamples

Pāhoehoe HIGH LOW LOW DARKBasaltGabbro

ʻAʻā LOW HIGH HIGH LIGHTGraniteRhyolite

Pegmatite