Geology Ch. 4

Which of the following are the two characteristics that we use to classify igneous rocks? -Chemical (or mineral) composition. -The way the rock feels to the touch. -The size of the mineral crystals within the rock (the texture). -The location the rock was found. -The size of the rock.

-Chemical (or mineral) composition. -The size of the mineral crystals within the rock (the texture).

The igneous rocks granite and gabbro have large minerals. In which location would they have formed? -deep in the crust - on the surface

-Deep in the crust

Which will cool faster? -magma deep underground -lava erupted onto the surface

-lava erupted onto the surface

The phaneritic mafic rock name is ___ and the aphanitic mafic rock name is ___ .

gabbro, Basalt

A rock's texture refers to

the size, shape, and arrangement of the mineral components.

Porphyritic andesite. Two students are debating about the cooling rate of this rock, and the formation of the large white minerals. Which student has made a correct statement? 1. This is an igneous rock, so everything started off as magma. The large minerals must have formed deep underground when the magma was cooling slowly, like in a magma chamber. But the rest of the rock has very small minerals, so they cooled quickly at the surface. 2. The magma must have gotten large pieces of sediments that we can see trapped in it, and the sediments didn't melt, even though they were in the magma. So, this rock formed because large pieces of sediment got picked up by lava, and then that lava cooled quickly.

1.

Fast cooling will form what kind of texture?

Aphanitic

Two igneous rock textures that can be found in extrusive igneous rocks include ___ and ___ .

Aphanitic, Glassy

Choose all the rocks from the following list that are extrusive: Basalt Rhyolite Obsidian Andesite Gabbro Granite

Basalt Rhyolite Obsidian Andesite

The two intermediate rocks contain the same minerals. They are: Na-rich plagioclase Ca-rich plagioclase Ca/Na plagioclase Pyroxene Quartz Amphibole Olivine K-feldspar (potassium feldspar)

Ca/Na-rich plagioclase Amphibole

The phaneritic intermediate rock name is ___ and the aphanitic intermediate rock name is ___ .

Diorite, Andesite

Quenching will form what kind of texture?

Glassy

Which of the following rocks formed deep in the crust? (You may choose more than one answer.) Granite: Gabbro: Rhyolite: Basalt:

Granite Gabbro

The phaneritic felsic rock name is ___ and the aphanitic felsic rock name is ___ .

Granite and Rhyolite

Choose all the rocks from the following list that are intrusive: Obsidian Granite Basalt Andesite Gabbro Diorite

Granite, Gabbro, and Diorite

The two felsic rocks contain the same minerals. They are: Ca/Na plagioclase Olivine Pyroxene K-feldspar (potassium feldspar) Ca-rich plagiclase Quartz Na-rich plagioclase Amphibole

K-feldspar Quartz Na-rich plagioclase

What is the most important characteristic of a glassy texture?

Lack of crystals

Volcanic

Lava cooled on the earth (extrusive)

What is the difference between mafic, intermediate, and Felsic

Mafic- rocks are composed of 50 percent silicon dioxide Intermediate- rocks are composed of 60 percent silicon dioxide Felsic- rocks are composed of 70 percent silicon dioxide

Plutonic

Magma cooled in the earth (intrusive)

The phaneritic ultramafic rock name is ___ and the aphanitic ultramafic rock name is ___ .

Peridotite, komatiite

What is the difference between aphanitic and phaneritic?

Phanaretic: have the course grain look of the rock and have large crystals that you can see without a microscope. Aphanitic: have crystals that you cannot see without a microscope.

Slow cooling will form what kind of temperature?

Phaneritic

Which igneous rock texture is found in intrusive rocks?

Phaneritic

Slow cooling in a magma chamber followed by eruption and fast cooling at the surface will form what kind of texture?

Porphyritic

Which of the following textures contains phenocrysts and groundmass?

Porphyritic

What is the most important characteristic of a vesicular texture?

Presence of air filled cavities

The two mafic rocks contain the same dominant minerals. They are: Pyroxene K-feldspar (potassium-feldspar) Amphibole Olivine Ca-rich plagioclase Na-rich plagioclase Ca/Na plagioclase Quartz

Pyroxene Olivine Ca-rich plagioclase

What is the most important characteristic of a porphyritic texture?

The two different crystal sizes

The igneous rocks rhyolite and basalt have minerals so small it is difficult to distinguish them with the naked eye. In which location would they have formed? deep in the crust on the surface

on the surface