Name __________________________
Period ________
Rocks and the Rock Cycle
I. Rocks
1. Nearly all rocks are composed of one or more ____minerals___. For
example, granite is a rock which is composed of the minerals,
___quartz____, ___feldspar___, __hornblende___, and
__biotite mica _.
2. Geologists classify rocks according to how they were __formed___.
a. __igneous___ rocks form when molten rock, known as magma (or lava
if it reaches the surface), cools and solidifies.
b. ___sedimentary___ rocks usually result from the __compacting____
and ____cementing____ of layers of sediment (sand, silt, clay, mud,
gravel).
c. __metamorphic____ rocks form when rocks get changed by heat
and/or pressure without melting.
II. Formation of Igneous Rocks
1. Igneous rocks form by the _____crystallization______ (liquid to solid) of
molten magma or lava.
2. The size of the crystals provides a clue to how ______quickly_____ the
rock solidified.
a. Slow cooling allows the molecules enough time to form ___large____
crystals (intrusive).
b. Rapid cooling produces rock with crystals too ___small____ to be
visible (extrusive).
c. Volcanic glass (obsidian and pumice) cools so quickly that the crystals
do not have time to ___form_____.
3. Classification
a. Igneous rocks are classified using just two characteristics:
____crystal size____ (texture) and ___color_____.
b. The scheme for identifying igneous rocks is on page ___6__ of your
ESRTs.
c. Light colored rocks are usually rich in feldspar (fel) and silica (like
quartz), so they are called ______felsic_______.
d. Dark colored rocks contain more minerals rich in magnesium (ma) and
iron (Fe), such as amphiboles (hornblende), pyroxene, so they are
called _____mafic________.
e. Even though obsidian appears _____black____, it is felsic.
III. Formation of Sedimentary Rocks
1. Most sedimentary rocks are composed primarily of the ____weathered_____
remains of other rocks.
2. Sedimentary rocks usually form by the ____compacting______ and
____cementing______ of particles of ____sediment____ (sand, mud, silt,
clay, gravel, shells).
3. Grains of sediment are usually rounded by abrasion (like sand-blasting) and
deposited (settling to the ground) in ______layers_______.
a. _____Layering_____ in sedimentary rocks is helpful in distinguishing
them from non-sedimentary rocks.
4. Although sedimentary rocks are the most common rocks that you see at the
surface, they exist as a relatively ______thin_____ layer over metamorphic
and igneous rocks.
5. Characteristics
a. The most common sedimentary rocks are the ___clastic______
(fragmental) rocks, which are made up of different ___sized______
particles or fragments.
b. The second group of sedimentary rocks is called ___crystalline_____
and form by precipitation (settling) of materials from solution in
____sea water_______. Dolostone, rock _____salt____, and rock
___gypsum______ are some examples.
c. The third group of sedimentary rocks is called the ___bioclastic____
sedimentary rocks, which are the result of ancient plant and animal
remains. _____coal_____ and some ___limestone______ are examples
of bioclastic sedimentary rocks.
d. The classification scheme for sedimentary rocks is on page ___7___ of
your ESRTs.
e. Sedimentary rocks for at or near the ____surface___________.
f. Fossils are found almost ____exclusively________ in sedimentary
rocks (rarely do igneous or metamorphic rocks have fossils).
IV. Formation of Metamorphic Rocks
1. Metamorphic rocks form when sedimentary, igneous, and metamorphic rocks
are changed by _____heat________ and/or ____pressure______.
a. There is no ____melting_______ involved in the formation of
metamorphic rocks, only ___re-crystallization_____ of crystals
(minerals).
2. Metamorphic changes include ___crystal____ growth, the formation of new
______minerals______, and an increase in ____density_____, and the
distortion of structures (such as the layering).
a. Metamorphism often results in the alignment of crystals (minerals),
known as ____foliation_______. The following are examples in order
of increasing foliation: slate, ___phyllite____, and schist.
b. The most intense foliation shows a separation of minerals into light
and dark layers, known as _____banding_____. An example is
______gneiss_______.
3. Most metamorphic rocks are formed _______deep______ within the Earth.
For example, the metamorphic rocks at the surface of the Adirondack
Mountains formed 20 to 30 miles deep within the Earth 1.1 billion years ago.
4. Classification – The classification scheme for metamorphic rocks is on page
____7___ of your ESRTs.
V. The Rock Cycle
1. The rock cycle is a model of ______natural______ changes in the rocks and
rock material. Rocks cycle through a variety of _______forms_______.
2. The rock cycle is found on page ____6___ of your ESRTs.
The rock types are in
blocks, the
intermediate states
(sediments and
magma) are in
ellipses, and the
processes are on the
arrows. Follow the
arrows from one rock
type to another to see
how they cycle.