Igneous rocks
Melting point
650-1150
magma mixing
intermittent pulses of magma may be injected into the magma chamber from the same or different sources over a long period of time. Magma thoroughly mixed so the individual component are no long recognizable
Magma
molten rock, underground
Bowens reaction series
-During crystallization, the composition of the liquid portion of magma continually charges due to removal of elements by earlier-forming minerals -silica component of the melt becomes enriched -minerals in the melt can chemically react and change
Components of Magma
1. Liquid (portion is mobile ions mostly of the 8 common elements) 2. Solid( minerals that have crystallized from the magma as it cools) 3. Gas (components that form a gas at surface pressure, but dissolved in magma.)
Felsic
A group of light coloured minerals including quartz, low silica content, low viscosity
Assimilation
Changing a magmas composition by incorporating surrounding host rocks into a magma
Describe how igneous rocks form
Extrusive igneous rocks cool and solidify quicker than intrusive igneous rocks. They are formed by the cooling of molten magma on the earth's surface. The magma, which is brought to the surface through fissures or volcanic eruptions, solidifies at a faster rate.
Fractional crystallization
First formed crystals in a cooling magma are segregated from remaining magma.
Explain what factors contribute to the resulting texture(grain size)of an igneous rock
Grain size, Temperature
Identify common igneous rocks based on a description of their texture and composition
Granite, Basalt
Explain the roles that heat, pressure, and water play in causing a rock to melt, and some major tectonic environments where each operate
Heat-Magma rises it brings heat with is, the heat rises the temperature of the surrounding crustal rock, which can cause it to melt. Water- when volaties mix with hot, dry rock they break chemical bonds which cause the rock to melt. (subduction) Pressure- Pressure prevents melting because of the weight of overlying rock and the pressure prevents atoms from breaking free from solid mineral crystals. So a decrease in pressure is what causes it to melt.
Extrusive
Igneous rock cool ON earths surface rapidly & therefore have finely crystalline texture (<1mm) EX: basalt, Rhyolite
Intrusive
Igneous rocks cool BELOW earths surface slowly, therefore have a coarsely crystalline texture (>1mm) EX: granite&Gabbro
lava
Molten rock on earths surface
Relationship between rate of cooling and grain size
Slowing cooling rate- More time for crystal growth-longer crystals faster cooling rate- less time for crystal growth- smaller crystals
Compare igneous rocks that form below Earth's surface with those that form above Earth's surface.
The magma cooled slowly and formed intrusive igneous rock. As magma pushes up toward Earth's surface, it makes channels and other formations underground. Formations of intrusive igneous rock can be harder and more lasting than other types of rock.
Describe how igneous rocks are named based on their texture and composition (minerals that make up the rock)
The most general classification is based on the relative abundance in a rock of felsic (feldspar and silica-quartz) minerals vs mafic (magnesium and ferrum or iron) minerals.
Decomposition melting
The process of decompression melting involves the upward movement of the earth's mantle to an area of lower pressure. The reduction in overlying pressure enables the rock to melt, leading to magma formation
Explain how cooling rate affects the resulting crystal size of minerals within igneous rocks.
When magma cools, crystals form because the solution is super-saturated with respect to some minerals. If the magma cools quickly, the crystals do not have much time to form, so they are very small. If the magma cools slowly, then the crystals have enough time to grow and become large. Some granites contain minerals which are up to one meter (3 ft) across!
Mafic
a group, of dark-coloured, mainly ferromagnesian minerals, high silica content, high visocsity