Chapter 3 - Igneous Rocks Flashcards
Igneous rock
Formed from the cooling and crystallization of magma.
Sedimentary rock
Formed when weathered fragments of other rocks are buried, compressed, and cemented together, or when minerals precipitate directly from solution.
Metamorphic rock
Formed by alteration (due to heat, pressure and/or chemical action) of a pre-existing igneous or sedimentary rock
Rock cycle
Shows how the 3 rock types transform into one another.
There are two forces:
1. Earth’s internal heat engine, which moves material around in the core and the mantle, and leads to clow but significant changes within the crust.
2. The hydrological cycle, which is the movement of water, ice and are at the surface, and is powered by the sun.
Intrusive igneous rock
When magma cools slowly within the crust over centuries to hundreds of years.x
Extrusive igneous rock
Erupts to the surface and cools quickly, in seconds to years.
Sediments
The weathered material (small rocks and mineral fragments) that are eroded, transported and deposited.
Partial Melting
When only part of a rock melts - this happens because rocks are not pure. Most rocks are made of several minerals, each having a different melting point.
Decompression Melting
Takes place within Earth when a body of rock is held at same temperature, but pressure is reduced. If a rock is hot enough to be close to melting point and is moved towards the surface, the pressure is reduced, and the rock can move to the liquid side of its melting curve.
Flux Melting
If a rock is close to its melting point and water is added, the melting point is reduced and partial melting occurs.
Polymerize
Si and O combine to form silica tetrahedra and as cooling continues, they link together to form chains.
Bowen Reaction Series
The sequence in which minerals crystallize from magma.
Created by Canadian petrologist Normal L. Bowen.
Gabbro
Magma becomes Gabbro when cooling slowly underground.
Basalt
Magma becomes Basalt when cooling quickly at the surface.
Fractional Crystallization
When crystals form and settle in the magma chamber, making the mafic magma more of a felsic magma due to the loss of iron and magnesium to the crystals.
Porphyritic
A texture of rock when there is significant different in crystal size, where larger crystals are at least 10x bigger than the average smaller crystals.
Phaneritic
Having crystals that are large enough to see by eye - >0.5mm
(From Greek: “visible”)
Aphanitic
Crystals too small to distinguish.
(From Greek: “unseen”)
Country rock
A native rock to a region in contrast to any intrusion of viscous geological material (magma).
Stoping
When a fragment of country rock breaks and falls into magma. The resulting fragments of this event are called XENOLITHS. (From Greek: “strange rock”)
Xenolith
The resulting rock formation when a country rock fragment falls into magma.
Pluton
When upward moving magma cools within the crust.
Stocks
Large irregular shaped pluton, exposure to surface is < 100 km sq.
Batholiths
Large irregular shaped pluton, exposure to surface is > 100 km sq.
