Geo Lab 3 (Igneous Rocks)

Rocks

aggregates of crystals or grains of one or more minerals

Igneous, Sedimentary, or Metamorphic

Rocks are classified as _______, ________, or ________ based on how they are formed

Igneous Rock**

solidified from melted rock

Sedimentary Rock

formed from material (sediment) deposited on the Earth's surface

Metamorphic Rock

formed when preexisting rocks recrystallized, as solids, under high temperature and pressure beneath Earth's surface

Rock Cycle

This global rock recycling program is called the _______ ______

sedimentary and metamorphic

Igneous Rocks convert to _______ and _______ rock

igneous and metamorphic

Sedimentary rocks convert to ______ and ______ rock

sedimentary and igneous

Metamorphic rocks convert to ______ and ______ rock

magma

Volcanic eruptions happen when molten rock, called _______, rises to the surface

lava

The magma then either flows onto the surface as ______ or explodes at the surface

extrusive

Igneous rocks that cool on the surface are called _______ rocks

intrusive

Igneous rocks that cool beneath the surface are called ______ rocks

1. to understand volcanoes likely future eruptive style
2. to understand how our crust formed
3. to learn about Earth's history
4. metal ore deposits

Reasons igneous rock is studied:
1.
2.
3.
4.

Texture

refers to the size, shape, and arrangement of the crystals or grains composing a rock

crystalline

All igneous rocks have a _______ texture

Thin sections

Very thin, transparent slices of rock

Coarse grained (phaneritic)

An igneous texture in which nearly all crystals are large enough to be seen without a hand lens

Fine grained (aphanitic)

An igneous texture in which most crystals are to small to be recognized with the unaided eye

Glassy

Describes igneous rocks that are made of glass and lack crystals

Pegmatitic

Describes igneous rocks with exceptionally large crystals

Porphyritic

An igneous texture in which crystals of two different sizes are present in the same rock

phenocrysts

groundmass

Porphyritic: the larger crystals, called _______, are surrounded by many smaller crystals, called the __________

Vesicular

vesicles

________: bubbles that form in lava and neither pop nor escape can be frozen into the lava; the cavities left behind are called _______

Pyroclastic

_________: explosive volcanic eruptions expel a lot of gas, glassy volcanic ash, lava, and fragments of rocks and minerals

pyroclasts

pyroclastic texture

Pyroclastic: the resulting deposit contains a lot of shattered volcanic glass, rock, and mineral fragments called ________, that define a _______ _______

tuff

pyroclastic breccia

An extrusive igneous rock with a pyroclastic texture is called a ____ if the pyroclasts are LESS THAN 6.4cm or a _______ if they are 6.4cm or more

mafic

Most dark colored igneous rocks are rich in calcium plagioclase and iron magnesium, they are called _____

Ultramafic

________ rocks are composed almost entirely of iron magnesium

felsic

Light colored or ______ igneous rocks commonly contain potassium feldspar

Intermediate

_________ igneous rocks are neither dark nor light

1. the concept of PARTIAL MELTING

2.partial melting takes place at plate boundaries

What happens at plate boundaries that allows magmas to form:

Partial Melting

when some minerals melt but others stay solid