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Rocks
I. Rocks are aggregates (mixtures) of minerals or simply large samples of one mineral.
1. Usually, rocks are ____________________________(have more than one mineral), such as
granite.
2. Rocks are NOT identified using the tests you used for mineral identification.
3. The minerals in rock help determine the name of the rock.
4. The ______________________ of the rock determines which TYPE of rock it is.
II. There are 3 main categories (types) or rocks:
1. _____________________________ (‘fire’ rock) Links to Animations
2. _____________________________(rock from particles of other rocks,
etc)\\Vc_hs\vol1\Users\HS\students\JMCMAHON\grand canyon.htm
3. _____________________________ (rocks that have ‘changed form’)
III. Igneous rocks igneous pix
1. Igneous rocks are called ‘fire rocks’ because they form from ________________ or
__________________________.
2. Magma is called __________________________________ because that is where the
elements come together that will form minerals as magma cools.
3. Igneous rocks are called the _________________________________ of all others.
4. All igneous rocks have ____________________________________, because they form as
the magma cools, and each crystal grows into the ones around them. Some crystals are so
small that we can’t see this without the use of a ___________________________
_____________________________.
5. Igneous rocks are classified (see page 6 of ESRT) according to:
a. the _________________________________ of the rock, which is determined by
the magma or lava that forms the rock. As old rock pushes down into the mantle
and melts, it mixes with magma that is already there, forming slightly different
magma. Over time, different igneous rocks have formed. Minerals have different
colors, and these colors help identify the type of igneous rock.
b. the _____________________________ or grain size of the rock, which is
determined by how quickly or slowly the magma cools to form rock.
c. Together, mineral composition and texture identify the rock.
6. In the ______________________________________, the melting points for common
igneous minerals are shown. Minerals with high melting points form crystals
_______________________, while those with low (cool) melting points (typical of crust
closer to the surface) forms crystals __________________________.
7. When the magma cools deep below the ground, it is called ___________________or
plutonic, and the minerals formed will be ____________________grained.
When the magma cools NEAR the surface, much more ______________________, the
crystals don’t have much time to form and the rock is called ___________________ or
volcanic, and the minerals will be ____________________________ grained. Glassy
minerals form _______________________________________.
8.
The three main igneous families, _____________________, ____________________and
basaltic are described in the lab and lecture and text. The families are identified according to
the type of ______________________________ from which they form, which are
characterized by the minerals and color.
a. The GRANITE family, formed from _____________________ magma, makes up
the CONTINENTAL CRUST, which is low density (_______________) compared
with the ocean crust (_______________).
b. The _________________________ family, formed from _______________
magma, makes up the ocean crust. Its density explains why
___________________________________________
c. The third family is the _____________________________ family, which comes
from magma that is a mixture of both mafic and felsic minerals, therefore its
minerals have characteristics of both granites and basalts.
9. Porphyritic textures refer to igneous rocks that have VARIOUS sized minerals, like a
chocolate chip cookie. This happens when the magma _______________________ in
stages.
10. In summation, Igneous rocks are identified in the lab by comparing their:
_______________________________, which tells you what minerals are in it, and
therefore what magma it came from and the ______________________________, which
indicates whether the rock cooled quickly or slowly (extrusive or intrusive).
IV. Sedimentary rocks
1. Form from ‘pieces’ or _________________________________ of other rocks, or from
chemical or biological processes. Identified by _____________________, lithification
(how they formed) and composition.
2. While igneous rocks reach down many miles beneath the crust, sedimentary rocks form a
thin ____________________________ on the top of earth’s ________________________,
because these rocks form (mostly) when pre-existing rock is ________________________
by exposure to weather and the pieces are dumped in one place and pile up over time.
3.
Rocks that form from weathered pieces of other rocks are called ___________________
rocks.
Clastic rocks (see page 7 of ESRT) are named according to the
_____________________ of the particles/sediments from which they are made. Small
particles are often __________________________ together, while it takes
____________________________ to hold larger particles together in the
____________________________________, breccias and some sandstones.
4. Most sedimentary rocks form in _________________________ because rivers carry the
sediments and then drop them as they slow down when entering an ocean or lake. The
particles drop according to ____________________ , and in layers. This layering is called
____________________________________ .
5. Clastic sedimentary rocks may have particles that are from MANY different types of other
rocks and the particles may be of many different AGES. The youngest part of any
sedimentary rock is the ___________________________ that holds it together, but the
rock is ___________________________ than any particle in it.
6. Non-clastic sedimentary rocks come from two processes:
a. _______________________ or biological (coal and shell limestone)
b. Chemical (precipitates and _______________________)
i. ________________________, such as chemical limestone, occur when ions
come together and fall to the bottom as a new substance.
ii. Evaporites, such as halite and gypsum, form when shallow seas
____________________________, leaving the minerals behind.
7. Fossils are usually ONLY found in sedimentary rock, commonly in shales, siltstones and
limestones. Only the gentle layering of sediments can preserve the imprint of a fossil.
Igneous rocks come from __________________________, which ruins the imprint, as does
the partial melting that occurs when ______________________________ rocks form.
V. Metamorphic Rocks
1. These form when pre-existing rocks are ______________________________ due to heat
and pressure.
(If the old rock melts, then it does not become metamorphic, because melted rock produces
magma and igneous rock).
2. Metamorphic rocks are _______________________________ versions of pre-existing
rock. The minerals often just line up differently. Intense metamorphism will really change
the minerals, too.
3. Metamorphic rock are classified according to:
a. The presence or type of _________________________________, which is seen by
observing the texture of the rock. This must be observed in lab and using pictures.
b. The second identifier is the composition of the rock, especially when discussing the
non-foliated rocks. For example, marble and quartzite look a lot alike, but are made
of very different minerals. (the _______________________________ test
identifies marble and a comparison of _________________________ shows which
is quartzite).
4. Rocks formed by intense pressure generally have the minerals align at a perpendicular to
the direction of the pressure. This often forms the _____________________ texture.
5. The type of foliation is described on page ________ of the _____________.
6.
Rocks formed by intense heat are often called _________________________________
rocks because they are usually bands of rock that are __________________________ due
to the presence of nearby lava or magma flows, which partially ______________________
the rock.
7. Contact metamorphic rock are found along igneous ______________________ as the
magma heats the rock. Zones of metamorphic rock usually are found between igneous
rocks and other rocks.
8. Identifying metamorphic rocks is pretty tricky, and requires patience (and sometimes a
good stereomicroscope)