Rock Families, Rock Forming Processes and Rock Textures Metamorphic rocks have m
Rock Families, Rock Forming Processes and Rock Textures
Metamorphic rocks have minerals formed from the process of recrystallization deep below Earth’s surface where under conditions of high pressure and/or high temperature. As minerals recrystallize the rock can also flow very slowly like hot taffy creating a texture or fabric in the rock called foliation. How is the foliation expressed in slideshowing foliation or foliated? There are two very common metamorphic rocks that can look similar and are not foliated. What are the names of these two rocks?
Even though the above two rock types look similar, they can easily be distinguished by a couple of easy tests (Note: this particular question is more for preparation for the Rock ID exam, not the Lecture Exam—I just thought I’d throw it in there].
What are the names for three Rock Families?
What is the difference between extrusive and intrusive igneous rocks? What is meant by plutonic vs volcanic rock? How do the first two terms equate to the second two terms?
What is the difference between magma and lava? (see slide number 15). How do these two terms relate to each of the terms mentioned in 3 above?
Know the difference between conglomerate and breccia.
On the field trip (at Millerton Point) there were alot of cobbles and pebbles of a type of biological (a.k.a., biogenic) sedimentary rock that was derived from Franciscan bedrock. It had the hardness of quartz. What was the name of the rock?
Limestone fizzes violently when you drop HCl on it because it is made up of tiny fragments of what kind of mineral? The term “Igneous” is derived from the Latin term ignis which means what?
A pyroclastic rock is an igneous rock that doesn’t form quite as directly from molten rock as volcanic flows or igneous intrustions. How do pyroclastic rocks form?
Understand the difference between “phaneritic” and “aphanitic”.
What is a phenocryst? When phaneritic or aphanitic rocks have phenocrysts how does this change the name of the rock? For example, if a granite or and andesite contains phenocrysts, they are still granite and andesite, but what term do we add to the rock names to denote that they contain phenocrysts?
Would a peridotite or a gabbro likely contain quartz phenocrysts? (this answer would be found in one or more of your igneous rocks handout). The minerals in igneous rocks all belong to what mineral class?
Be familiar with 4 or 5 of minerals that are usually found in granite.
What kind of igneous rock is pumice?
Know the difference between felsic rocks and mafic/ultramafic interms of relative Silica content, and relative collective concentrations of Na, K, and Al versus the concentrations of Fe and Mg. These concentrations are what distinguish these endmember rock types.
How does the relative lightness or darkness of color generally relate to differences in the composition of igneous rocks.
Be familiar with “Bowens Reaction Series” (slide number 30). Points to grasp: different mineral crystallize at different temperatures; the more mafic minerals (higher Fe and Mg, no Na and K) crystallize at higher temperatures. The felsic minerals (high K and Na content, lower Fe Mg) crystallize at much lower temperatures. Hence mafic magmas are much hotter than felsic magmas. Try to make sense of this for a multiple choice type question.
Be able to match images of the different types of igneous intrusions (slides 31-33 on PPT4), with their nemes .