Rocks 1 Flashcards
_____ are formed from solidification of magma or lava which flows out
from depth. There are two types of igneous rocks based on the temperature-pressure condition during the solidification of magma – extrusive and intrusive. In addition, the time duration is also a factor in the formation of crystals
of igneous rocks. Let us deal with this formation and types of igneous rocks in
detail.
Igneous rocks
Igneous rocks are characterized by intergrowth of crystals and/or volcanic glass. ____ is an indicator whether a rock is formed deep within Earth or just near the surface. It is directly proportional to the cooling rate of magma. This means that when the crystals are big, it denotes that the rock is formed deep underground since the magma has a longer trip to the surface giving it longer time to cool down at a very slow rate. On the other hand, magma cools quickly (fast cooling) near the surface that causes formation of smaller crystals since it is given few time to form.
Crystal size
An example of a rock with large crystal is a ____ while those with smaller crystals is an ___.
diorite,
obsidian
Crystals form when magma are cooled. A general model is created to show the
progression of silicate crystallization at specific temperature. It is called Bowen’s reaction series which is developed by petrologist ____.
Norman L. Bowen
The first one is the ____ shown
at the left side of Fig. 20.
-OPAB
The first mineral, olivine, will form if the chemistry of
magma (at about 1200 °C) has everything that these minerals need. If the magma is
allowed to cool down further, olivine will melt and create pyroxene which is the
next mineral in the sequence. Further cooling will form amphibole, and then biotite
mica.
discontinuous branch
On the other hand, the ____ does not include the transformation of different minerals. It only shows the development of calcium-rich plagioclase
feldspar to its sodium-rich counterpart.
continuous branch
Igneous rocks can be classified based on the temperature-pressure condition
during the solidification of magma: ___ and ____.
extrusive,
intrusive
An _____ forms when magma or volcanic fragments erupt and
solidify on Earth’s surface which results to very fine-grained rock with very small crystals that could not be seen through naked eye.
It is also known as a ____ rock.
The texture of most extrusive rocks can be of three different forms: smooth, full of holes, or can be with large crystals embedded in a fine ground mass.
extrusive igneous rock,
volcanic
Examples of extrusive igneous rocks are ____, ____, and _____.
obsidian,
andesite,
pumice
An ____ forms when magma crystallizes within the crust and is composed of medium to coarse grains. It is also known as a plutonic rock.
intrusive igneous rock
Generally, two types of intrusive bodies exist, namely: ___ and ____ type.
concordant,
discordant
When the pre-existing rock bed is cut across by an intrusive body, it is termed
as ____ while if it runs parallel to the bedrock, igneous rock bodies are called ____.
concordant,
discordant
Types of Igneous Rocks Based on Texture
Extrusive
___ rock has crystals that are too fine-grained to be seen by the naked
eye or even with the help of a hand lens/ crystals are so fine
Aphanitic
Types of Igneous Rocks Based on Texture
Extrusive
____ rock contains tiny holes called vesicles due to gas bubbles in the
lava or magma
Vesicular
Types of Igneous Rocks Based on Texture
Extrusive
_____ are rocks where larger crystals are embedded in smaller crystals/ contain
groundmass and phenocrysts
Porphyritic
