Igneous Rocks -

Phanaritic Texture

course grained

What are the four basic igneous rock compositions?

felsic, intermediate, mafic, and ultramafic.

magma

A molten mixture of rock-forming substances, gases, and water from the mantle

glassy texture

A term used to describe the texture of certain igneous rocks, such as obsidian, that contain no crystals.

aphanitic texture

A texture of igneous rocks in which the crystals are too small for individual minerals to be distinguished without the aid of a microscope.

porphyritic texture

An igneous rock texture in which large crystals are scattered on a background of much smaller crystals.

How does igneous rock crystalization occurr

As the magma begins to cool, the silica and oxygen combine and form silicon/oxygen tetrahedra crystals. These continue to bond together and continues to grow new crystal bonds that form with the tetrahedra, eventually forming a solid mass.

Felsic

Describes magma or igneous rock that is rich in feldspars and silica and that is generally light in color. quartz and potassium feldspar.

characteristics of felsic rock

Fel- felspare, sic - silicates, rich in silicates, come from magma

What are the four basic groups of igneous rocks in order of silica content.

Felsic, 70%, intermediate - andesitic, mafic, ultramafic (lowest silica)

How do light-colored igneous rocks differ from dark-colored rocks?

Felsic, or granitic. Dark is Mafic / Balsatic. Felsic - 10% dark minerals, Mafic is 45%+ Felsic - 70% silica, Mafic low as 40% Felsic - less dense, mafic - more dense Melts at a lower temp and more viscous Mafic melts as higher temps, less viscous

How do extrusive igneous rocks form?

From magma that cools as it reaches the surface of the Earth

what are the differences between intrusive and extrusive igneous rocks?

Intrusive - formed from magma underground at at high pressure, have large, formed crystals over long periods of time. Extrusive, formed from Lava, above ground, formed very quickly because they cooled quickly. Fine grains of crystals.

Difference between felsic and mafic igneous rock

Mafic rocks are darker and denser. At least 45% dark silicates such as magnesium and iron. MAfic forms basalt.

what are the components of magma

Melt, solid components, volatiles

vesicular texture

Rock that has a spongy appearance due to trapped gas bubbles in the lava.

What is crystallization in the magma process?

The process by which atoms are arranged to form a material with a crystal structure

where can intrusive igneous rocks be seen?

Yellowstone, Mount Rushmore, Stone Mountain, Georgia

granitic composition

a compositional group of igneous rocks that indicate a rock is composed almost entirely of light-colored silicates, mainly quartz and feldspar and commonly create granite

pyroclastic texture

a fragmental texture characteristic of igneous rocks composed of pyroclastic materials

Texture of a rock

based on size, shape and arrangement of mineral grains. Reveals the environment from which the rock was formed.

volatiles

gaseous components of magma dissolved in the melt. They will readily vaporize at surface pressures

Igneous Rock Textures

glassy, aphanitic, phaneritic, porphyritic, pyroclastic, vesicular

Peridotite (Igneous)

has olivine in it. phaneritic ultramafic peridotite is the main constituent of the upper mantle

lava

molten rock that erupts on earth's surface.

most common elements in earth's crust

oxygen, silicon, aluminum, iron, calcium, sodium, potassium, magnesium

Light (Nonferromagnesian) Silicates

quartz, muscovite mica, and feldspars created with more potassium, calcium and sodium

intrusive igneous rock

rock formed from the cooling and solidification of magma beneath Earth's surface - Plutonic. Can be seen because erosion -

extrusive igneous rock

rock that forms from the cooling and solidification of lava at Earth's surface - Volcanic Rock

igneous rock

rock that forms when magma cools and solidifies

dark silicates - ferrogamnesian

silicate minerals containing ions of iron and/or magnesium in their structure; also called ferromagnesian silicates Olivine, pyroxene, amphibole, and biotite mica are the common dark silicate minerals of Earth's crust

andesitic composition

the composition of igneous rocks lying between felsic and mafic. Intermediate rocks contain at least 25 percent dark silicate minerals—mainly amphibole, pyroxene, and biotite mica—with the other dominant mineral being plagioclase feldspar. This important category of igneous rocks is often associated with volcanic activity on the seaward margins of continents and on volcanic island arcs such as the Aleutian chain.

Factors that influence the texture of igneous rocks

the rate of cooling the amount of silica present in the magma, the amount of dissolved gases in the magma. Rate of cooling most important - rocks that cool slowly under pressure (intrusive) have larger crystals.

volatiles most commonly present in magma

water vapor, carbon dioxide, sulfur dioxide