lab 4 rocks cycle (1)
pdf
keyboard_arrow_up
School
University of Florida *
*We aren’t endorsed by this school
Course
1150L
Subject
Geology
Date
Apr 3, 2024
Type
Pages
5
Uploaded by ConstableSeahorse3916
GLY1150L Field Trip to Santa Fe C.C Jean Klein Rock-cycle garden. NOTE: This Lab is
not necessarily about getting the right answers, but it is about making observations and
exploring some of your thoughts.
IGNEOUS SECTION:
Stop 1.
This sample is a mafic igneous rock, most likely a gabbro which is an intrusive
(also known as plutonic), mafic igneous rock. How can you tell this is mafic? What is an
intrusive igneous rock?
I can tell this rock is mafic because it is dark in color and gritty. An intrusive igneous rock
is a rock formed by being trapped deep inside the earth as they go above the surface.
Describe the texture of this rock (how big do the individual mineral grains seem)? How
do you know it's intrusive?
The rock is very gritty and has thinner mineral lines within it. The lines are lighter as
well. I know it’s intrusive because of the color of the mineral grains. Being dark means
that the rock was not cooled by water like how extrusive rocks are.
Stop 2.
This sample is a pegmatite, another intrusive igneous rock. This one is felsic.
Compare this rock to the rock in stop 1 in terms of color and texture. What makes this
sample a pegmatite (hint: look up the def!)?
This rock compared to the rock in stop one is a lot lighter colored than the first one. Also
the mineral lines are different colors like reds instead of just white. This sample is a
pegmatite because of the course gigantic grained igneous rocks.
Stop 3.
This sample is a metagranite, an igneous rock that has been metamorphosed.
Granite is a felsic igneous rock that cooled slowly within Earth’s crust (a plutonic rock).
There is some very clear foliation (planar alignments of minerals) defined by the black
mineral. This is the observation that indicates that this rock may be metamorphic.
The granite has large lines of minerals and cool discoloration. Also very sharp edges
making it a very hard rock compared to others.
Stop 4.
These samples are all felsic extrusive (a.k.a. volcanic) rocks. Felsic is a
compositional term meaning corresponding to magmas/rocks that are rich in silica
(SiO2), potassium, and sodium; volcanic indicates that the magma cooled quickly after
eruption onto the Earth’s surface). Though they have different textures, they are
essentially the same composition. One rock is called obsidian (dark, smooth, glassy
texture) and another other is called pumice (rough, frothy-looking texture). Compare the
texture of these rocks to those in stops 1 and 2. How do these two rocks differ in
texture from those in stops 1 and 2? Hypothesize what might account for those
differences.
The colors of these rocks are completely different from stop 1 and 2. These rocks are
dark black and consist of very little mineral lines and instead offer holes where the air
bubbles have cooled. I think the difference that these rocks have are because the area
and how fast they cooled as magma are different.
Describe the appearance of both the obsidian and the pumice and hypothesize what
igneous processes may account for the difference in appearance.
Obsidian is very dark and hard with almost a shiny exterior. Pumice is more similar to
rock 1 and is more gray in color but still has the bubbles obsidian has. I think these are
different in appearance based on what part of the magma is cooled and how fast it
cools.
Stop 5
. This sample is a very fine-grained shallow intrusive, or perhaps extrusive rock.
Note the overall color of the rock. Gabbros are mafic rocks (low in SO2, rich in Ca, Mg,
And Fe). Typically, mafic igneous rocks are darker in overall color than felsic rocks. Is
this “color” generalization consistent with your observations at the previous stops? How
does cooling rate affect igneous rock texture?
The color of this rock is more of a brown color, not the darkest or the lightest. This rock
does seem to generally apply to the guidelines of overall rocks in the previous stops.
Cooling affects the texture of igneous rocks by how fine or course they end up
becoming.
Stop Number__
|
__Rock Name____
|
___Intrusive or Extrusive?
1
Gabbro
intrusive
2
Pegmatite
intrusive
3
Granite
intrusive
4
Volcanic glass
extrusive
5
Basalt
extrusive
SEDIMENTARY SECTION
Stop 6
. This sample is a
conglomerate
(a coarse-grained clastic sedimentary rock).
Describe the texture of this rock(Is there any obvious layering?)About how big are the
clasts (particles) that make it up? (Inches? Feet? Millimeters?) Are the rock fragments
smoothed and rounded or sharp and angular? How Variable is the size of individual
particles (clasts) that make up this rock? (Are they all about the same, a little variable,
highly variable?)
This rock is very grainy, there are a lot of smaller rocks within the large one. The
particles that make up the rock are very large and pebble-like around 1-2 inches. The
rcom fragments are smooth and rounded not sharp.The sizes are all about the same of
what make up this rock.
Stop 7
. This sample is sandstone (another clastic sedimentary rock made of
sand-sized clasts. Is there any obvious layering? About how big are the clasts
(particles) that make it up? Are the rock fragments smoothed and rounded or sharp and
angular? Compared to stop 6, how variable are the sizes of individual particles (clasts)
that make up this rock?
There is some layering but not a lot. Most of the particles that make the rock up are very
small with some discoloration from different things. The rock fragments are sharp
compared to other rocks. Also the sizes of the particles are smaller than stop 6.
Stop 8
. This sample is sandstone. Note the ripple marks on the top. What kinds of
environments do ripple marks occur today? Try to name one? Applying
uniformitarianism, what might you infer about the environment in which these sediments
accumulated before they were lithified into a rock?
I think the ripple marks are due to water and erosions from water. This can be do to
sitting in lakes or streams. I think that these sediments were probably joined together
from being washed down a stream and compacted together.
Stop 9.
This sample is shale (another clastic sedimentary rock made of accumulated
mud---silt and clay). Note the very fine layering. Is there any obvious layering?About
how big are the clasts (particles) that make it up compared to the previous 3 stops? In
which kind of environments does mud accumulate today? How do you think the overall
energy of moving water in this environment compared to the environment for stop 7?
There is a lot of obvious layering. It is just very fine, meaning a lot of different layers.
The particles are about the same size or smaller compared to the other three rocks.
Mud is in a lot of environments today but mostly in areas with water. I think there was
less energy in this stop then in stop 7.
Stop 10
. This sample is a coquina, a bioclastic rock type commonly found around Fl.
NE coast (the St. Augustine formation). How does this sample differ from the previous
sedimentary rocks? How is it similar?
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
This sample is harder and has larger grain pieces then the other samples. It is similar in
color to the sandstone but has more layers and bubbles then the sandstone did. They
are also all created near water.
Stop 11
. This sample is a limestone, a chemical sedimentary rock. Note the different
types of corals. How does this sample differ from the sedimentary rock at stop 9? How
is it similar the sedimentary rock at stop 9? In what type of environment did this rock
likely form? What observation led you to this conclusion?
This is different from the rock at stop 9 because it has many sharp edges and layers. It
is also made of different materials. It is not really similar to rock 9 at all besides being
made in similar ways. I think rock formed in the ocean or on the shallow sea floor. I think
this because I feel as if sand has gotten into the rock in areas and great the different
holes and layers.
Stop 12
. This sample is another limestone (a very common rock type in FL). It is a
piece of the Ocala limestone which is a part of the Floridan Aquifer, one of Florida’s
main sources of groundwater. What properties of this sample make it a good aquifer
material (a material that can store and transmit a lot of groundwater. How does this
sample (Stop 12) differ from the sedimentary rock at stop 10?
There are lots of holes and edges for water to glide through making it a good aquifer.
This sample is different from the rock at stop 10 because the texture is more rigid and a
slightly different color than in sample 10.
Stop 13
. This sample is a weathered quartzite…metamorphosed sandstone. It is made
almost entirely of recrystallized quartz. While many metamorphic rocks exhibit foliation
as a consequence of metamorphism, quartzite typically does not. (Note the lack of a
freshly broken, i.e. unweathered, surface makes it hard to distinguish features in this
rock.) Why would well-defined foliation not be common in metamorphosed sandstones?
I think there is no well-defined foliation in metamorphosed sandstones because of the
level they are buried. I don't think they are buried deep enough.
Stop 14
. This sample is a gneissic marble. Note the foliation. What mineral is the
majority of this rock made from? What other minerals, if any, can you see in this rock?
Are pure marbles (i.e. made completely from carbonate, with no impurities) commonly
foliated? Why/Why not? Is this rock igneous, metamorphic or sedimentary?
This marble is mainly made of limestone, but it also has some clay and such in it as
well. Most marbles are typically not foliated although there are exceptions. Marble is
primarily limestone therefore it is primarily a sedimentary rock.
Stop 15.
This sample is augen gneiss, with biotite schist inclusions (both metamorphic
rock types). Augen is German for eye, and it is called this because of the large
lens-shaped minerals grains within the rock. Try to identify the mineral that makes the
“augens”? In which other rock(s) did you see this mineral previously? Hypothesize
whether this metamorphic rock started out as an igneous or sedimentary rock? What
observation led you to this hypothesis?
I think there is quartz in the Augen Gneiss rock as well as maybe some mica. There has
been many rocks with similar materials but the most similar was granite or stop 3. I think
thai rock started off as an igneous rock because of what it is primarily made out of and
then became a sedimentary rock.
Stop 16.
This sample is a gneiss. Note the foliation, once again. Gneisses are very
high grade (intensely) metamorphic rocks. Hypothesize whether this rock started out as
an igneous or sedimentary rock? What observation(s) led you to this conclusion?
I think thai rock started off as an igneous rock because of what it is primarily made out
of and then became a sedimentary rock. I think it became a sedimentary rock based on
the way it is shaped now and the new materials it has gained.
Stop 17.
This sample is a migmatite. Note the folding. A migmatite forms when a rock
is metamorphosed so much that it begins to melt. There is granitic melt (white material)
which moved and re-crystallized. Is this an igneous rock or a metamorphic rock? Why?
I think migmatite is a metamorphic rock because it started off as a different kind of rock
but has been changed so such that it is now a metamorphic one.