Reference no: EM132814779

Question 1

(This section Is in the format of an Essay question, but there's no question. This is just tieing used as an informational section that will help you with questions later.)

Introduction

Geologists use composition and tex-turesto classify rocks. Different rocksform under different conditions, giving us an opportunity to piece together the ancient landscape and plate tectonic settings of the ancient Earth.This lab builds on the minerals lab (Lab #3) as students will apply what they learned in that lab to help identify new rocks.

Objectives
When you have completed this lab you should be able to:
1. Examine an igneous rock and determine whether it (a) crystallized slowly deep underground or (b) came out of a volcano and crystallized quickly on Earth's surface.
2. Identify common types of igneous rocks.
3. Describe how the characteristics of sediment grains change as they are moved further from their source.
4. Identify common types of sedimentary rocks and minerals in them.
5. Identify common types of metamorphic rocks and their characteristic textures,

Part I: Introduction to the Rock Cycle

All rocks can be put into one of three fundamentally different rock types: igneous, sedimentary, or metamorphic. This week, we will learn how geologists classify and name these different rocks.

Although any given rock formed a certain way and is named according to its characteristics (which reflect its formation history), this does not mean that any individual element or mineral within this rock has always been, or will always be, part of an igneous rock, for example. Instead, as plate tectonic and other Earth processes continue to operate over time, rocks will be weathered away, altered by heat and pressure, or melted to form magma. In this way, the elernentsthat make up any rock can ultimately be re-combined to form an entirely different type of rock. This connection between rock types is known as The Rock Cycle.

Watch this short animation film An Object at Rest" to have an idea about the rock cycle!

The diagram below depicts the processes that connect each type of rock via the rock cvc e Take a minute or two to study the diagram. At the end of this worksheet, after you learned everything about three types of rock, you will need to answer questions about rock cycle.

QUESTION 2
(This section is in the format of an Essay question, but there's no question This is just being used as an informational section that will help you with questions later )

Part II: Classifying Igneous Rocks
Igneous rocks are classified based on texture (grain size) and composition (color)

1. Texture (grain size)

The texture of an igneous rock refers to whether it formed on Earth's surface (extrusive or volcanic) or within Earth's interior (intrusive or plutonic). The size of the mineral crystals that form depends on the cooling rate. Extrusive rocks cool rapidly on Earth's surface and have small grains while intrusive rocks cool slowly underground and have large grains

Texture can be described as,
a) Fine grained (aphanitic): contain grains too small to see because crystals grow quickly under conditions of rapid cooling, typically in extrusive settings_ 13) Coarse grained (phaneritic): contain visible grains because crystals grow large by cooling slowly, typically in intrusive settings
c) Porphyritic: mixture of tine and coarse grains formed from a two-stage cooling process with initial cooling at depth and later cooling on the surface_ ch Vesicular: contains open holes representing trapped gas bubbles preserved in the rock due to rapid cooling.
e) Glassy: rocks made of solid mass of glass. Typically are black in color and have no visible mineral crystals due to rapid cooling.

2. Composition (Color)
The color of an igneous rock is a proxy for the amount of silica (Si02) present. Two terms are used to describe the amount of silica:
• Felsic: Silica-rick Contains silica-rich, light colored (white, pink, or translucent) minerals, such as quartz or feldspar.
• Mafic, Silica-poor Dominated by silica-poor, dark colored (black, dark-green) minerals, such as olivine, pyroxene, or amphibole_
To describe composition behveen or beyond these two end-members, following terms can be used:
• Intermediate: Contains approximately equal amounts of dark and light minerals and have a speckled appearance with.
• Ultramafic: rich in mafic mineral and very poor in silica.

QUESTION 3

Activity 1: Identifying igneous Rocks

For the following questions, use the Lab 4 information sheet and flow chart and the Rocks properties slidshows provided in the important information folder an IluskyCT to find the answers.

This rock is black in color and the mineral grains are really tiny. You can't really make any of them out without a magnifying lens. This rock has texture. The name of this rock is

QUESTION 4

This is a diorite. This rock has phaneritic texture because the crystal grains are (large, small) and (visible, non-visible). This indicates
that this rock is an (intrusive, extrusive) igneous rock. The coloration of the mineral grains has a salt-and-pepper character, and there's a lot of light-colored grains and a lot of dark-colored grains. The composition of this rock is (mafic, felsic, intermediate, ultramafic).

QUESTION 5

This rock is light in color. There are not a let of dark colored minerals that you can see. The composition of this rock is (mafic, felsic, intermediate, ultramafic). There are some visible flecks of mineral grains in the rock but the vast majority of grains in the rack are too small to see. This texture can be describe as (aphanitic, phaneritic), which also tell us that this is an extrusive rock. The name of this rock is

QUESTION 6

The minerals in this rock are almost exclusively dark in color. Most are black, some are a very dark greenish color. The composition of this rock can be described as (mafic, felsic, intermediate, ultramafic). The mineral grains are easily large enough to see and differentiate, indicating that this is a (intrusive, extrusive) rock. The name of this rock is

QUESTION 7
Igneous Rock 5 1 poi nts Save Answer

This rock is gray in color. Most of the mineral grains are too small to be visible, but there are a few larger white mineral grains that are visible. This is a/an

texture. The name of this rock is

QUESTION 8

Igneous Rock 6

Look at the rock below and read the description

"The minerals that make up this rock are mostly light in color. There are some that are darker in color but not very many. You can tell because the mineral grains are large and very easy to see.' In the text box below, provide:
1. The name of the rock described
2. Whether the rock is intrusive or extrusive
3. Whether the rock's composition is felsic, intermediate, matic, or ultramac

QUESTION 9

This is a Peridotite. The c inera Is composition of this rock is mostly pyroxenes and olivines. That is why this rack is dark green in color. The composition of this rock can be described as (rnafic, felsic, intermediate, ultramafici. Its grains are large and visible and therefore meet the criterion for being considered (phaneritic, aphanitic). indicating that this is an (intrusive, extrusive) rack.

QUESTION 10

Activity 2: Igneous Rocks and Tectonic Settings

Consider following 7 igneous rocks' basalt, andesite, rhyolite, peridotite, gabbro, diorite, and granite.

These rocks vary in both texture and composition. and these characteristics tell us the story of where and how they formed (I). For instance, rocks that form on the seafloor are typically darker in color because they are composed of darker, denser minerals (mafic), whereas rocks that form from magma in/on the continents are usually lighter in color because they have a greater proportion of silica (felsia
Furthermore, rocks that form deep underground cool slowly and thus have large crystals, whereas rocks that are formed as a result of volcanic eruptions cool quickly at the surface and have very small crystals often invisible to the naked eye.

Using the chart on the previous page, determine which rocks would be formed in each of the locations below. Write the name of each rock in the boxes provided. Hints:
• Pay close attention to whether the arrows are pointing at a surface location or an underground location, as this indicates slow or fast cooling!
• Volcanic eruptions associated with subduction zones can produce both intermediate and felsic magmas.
• Rocks that make up the mantle are ultramac

Match the igneous rocks to the locations in which they would form in the diagram below

QUESTION 11

Part Classifying Sedimentary Rocks

A sedimentary rock forms completely at the earth's surface and therefore records information about the earth's environment at the time and place the rock formed. its depositional environment. This makes sedimentary rocks very useful tools for interpreting earth history. During this week's lab, we will work on recognizing and interpreting the features in sedimentary rocks that help us unravel the rock's depositional environment.

Activity 1: Characteristics of Sediments

Clastic rocks are composed of sediments, which are rock and mineral fragments.

Observe the sediment in the two images below Be aware that the scales between the images are very different and that the image for Sediment B is more zoomed in than the image of Sediment A

In the text box below, identify 2 similarities and 2 differences.

QUESTION 12
What might be two reasons for the differences you observed in the images from the question above?

QUESTION 13
For the following questions (sediment 1-3), use the sediment images and descriptions below to identify the:
1. Sediment size name (e.g. gravel, fine sand, coarse sand, silt, clay, etc.)?
2. Sorting?
3. Rounding?

Sediment 1
Grains tit uniformly within a size range of 0.25 mm - 0.5 mm. All of the grains are colorless to white, have no apparent cleavage planes, and are harder than glass.

QUESTION 14
For the following questions (sediment 1-3), use the sediment images and descriptions below to identify the: 1_ Sediment size name (e.g_ gravel. fine sand, coarse sand, silt, clay, etc.)?

Sediment ranges in size between 0.5 mm and 2 mm. If you press your hand into this sediment you can feel a series of sharp points in the sediment The grains are mostly either white or pale pink. Many of the grains have two cleavage planes but some of the white grains do not have cleavage planes at all.

QUESTION 15
For the following questions (sediment 1-3), use the sediment images and descriptions below to identify the:
1. Sediment size name (e.g. gravel, fine sand, coarse sand, silt, clay, etc.)?
2. Sorting?
3. Rounding?
Sediment
Sediment is too small to easily see but through a magnifying lens you are able to tell that the grains are very uniform in size and are around 0.05 mm in diameter. Grains are pale pink in color and are harder than glass. They don't appear to have cleavage planes. You pick up some of this sediment and roll it around between you index finger and thumb. When you do this, you can feel some grit but the grains roll smoothly as you feel them move between your fingers which lead you to believe that the surfaces of the grains are smooth and not pointy.

QUESTION 16
Activity 2: Sediments characteristics and ancient environments
Differences in sediment shape, size, and sorting tell us about their transport to and character of depositional environments (where sediments are deposited). Well-sorted sediment is transported for a long time, over a long distance. High-energy environments, like a beach, also prWuce well-sorted sediment. Low energy environments drop fine grains out of suspension. Glacial deposits may contain particles that are as large as houses or as small as flour
Sediment shape indicates how much erosion the sediment has experienced. Well-rounded grains probably traveled far from their source; angular grains likely have a short transport lime.
In general, sediments deposited near their sources, soon after weathering, are composed of particles that are large, poorly sorted, and angular. Sediments deposited far from their sources, after a long history of movement, are composed of smaller, well-sorted, well-rounded particles.

The figure above shows the different depositional environments from mountains to deep seas. Fill in the blank next to each rock type with the letter of the appropriate depositional environment.
- A I. Sandstone
- v B II. Siltstone
- v C III. Conglomerate
- v D IV. Brescia
- V. Shale

QUESTION 17
Activity 3: Sedimentary Rock Identification
Sedimentary rocks can be divided into three fundamental types based on the materials involved and the process by which they formed: Clastic Chemical and Biochemical
Clastic:
composed of sediments, rock and mineral fragments.
• Chemical:
crystallized from solution as a result of changing physical conditions (e.g., evaporation). The most common solution is seawater but minerals are also dissolved in lesser concentrations in freshwater lakes on the continents.
As you saw in last lab, table salt is actually a mineral, halite. Salt forms when water evaporates because of increasing temperatures. As more water evaporates, the salt concentration in the remaining water rises to the point where the salt precipitates from the water and falls to the floor of a lake or ocean_ The salt is later buried under other sedimentary rocks_
• Biochemical:
formed by the actions or remains of living organisms. For example, the actions of organisms in seawater change the composition of the water causing the mineral calcite (the principal ingredient in limestone) to be precipitated from solution_ Massive limestone coral reefs in tropical oceans around the world have formed because of the actions of the coral organisms_ Other biochemical racks are composed of the remains of dead organisms. Chalk forms from the calcite skeletons of tiny marine organisms known as coccolithophores. In contrast, the shells of organisms that you might find on a beach may be broken down and sorted by wave action and cemented to form a shell-bearing limestone known as coquina_ Coal is also a biochemical rock formed from compacted remains of plants. It is common in tropical wetland environments where vegetation grew rapidly and was rapidly buried.

The sediments in this rock look like a bunch of fragments that have been cemented together. You can tell this because the grains do not fit neatly together and if you look with a magnifying lens you can see the cement material between them. Many of the grains are visible but all are smaller than 2 mm. This is a {elastic, chemical, biochemical) sedimentary rock. The name of this rock is

QUESTION 19
Observe the image below and read the description:
'It is difficult to visually pick out individual mineral grains in this rock. What grains you can see have apparently grown into each other which indicates to you that the minerals and the rock formed at the same time {i.e. the sediment did not previously exist as a series of fragments). As you handle this rock you find that it is easily scratched with a fingernail. You lick the rock and note that is does not taste salty. You apply HC1 acid to the rock and find that it does not react with the acid."

In the text bee below:
1. Identify these as being either clastm: chenuca: or biochemical sedimentary rocks
2. Use the Sedimentary Rock ID Km or the Rock Properties slideshow to name the rocks.

There are clamshells in this rock, indicating that it is a (clastic, chemical, biochemical) rock. Because of the presence of these clamshells you know that this rock formed in (glacial, desert, marine) environments. You feel a slight sense of accomplishment and satisfaction at having found these fossils (this has nothing to do with the rock, this is just what you feel in this scenario). The rock and the shells themselves both fizz vigorously when you apply HCI acid. What mineral could present in this rock?

QUESTION 20
This is a conglomerate. You can tell because the rock has many (rounded, angular) grains with the size larger than grains are harder than glass. You can see that the grains do not fit readily together and that they are held together with natural cement.

QUESTION 21

Sedimentary Rock 5
Observe the rock below and read the description:
This rock is black and lighter in weight than most rocks you've handled, On one piece you see what looks like a frond from a fern plant" In the text box below, provide:
1. This rock is clastic, chemical, or biochemical rock?
2. What would be the rock name?

QUESTION 22
The sedimentary grains that make up this rock are too small to see. You don't even feel much grit in the rock as you handle it. You apply HCI to the rock surface and nothing happened. You hit this rock with a hammer out of a sense of general frustration but find that when you do it breaks into a series of flat, sharp-edged chips. The name of this rock is (sandstone, siltstone, mudstone). Since the grain size is so small, this rock should be formed (close to/ far from) the mountains.

QUESTION 23

This rock is micritic limestone. It S a (Elastic, chemical, biochemical) rock. It is white in color. The mineral grains are very small but you can see with a magnifying lens that they interlock. if you apply HCI acid to this rock, will it fizz? (yes, no).

QUESTION 24

Part IV: Classifying Metamorphic Rocks
Metamorphism relates to changes in mineral composition and/or texture that occur in rocks as a result of increasing pressure and/or temperature and reactions with hot, mineral-rich fluids. These conditions will result in three possible changes in the rocks:
• Mineralogical some minerals recrystallize to larger grains, some convert to more stable minerals_
• Physical. high pressures can result in bent or folded rocks and distorted mineral grains.
• Fluids new minerals may precipitate from hot fluids to fill rock fractures and form veins.

There are two main types of metamorphism
1) Contact
when rocks undergo metamorphism because they come in contact with a heat source (usually a magma body). The composition does not change but the texture does. Marble forms when limestone is metamorphosed. Marble and limestone have the same composition, but marble has larger grains
2) Regional
when rocks undergo metamorphism usually associated with mountain building. In these areas rocks may be buried to great depths. Added pressure causes sheet-like minerals (mica) in the rock to rotate or grow in a preferred alignment. Those minerals are layered parallel to each other (like a stack of papers on a table) and perpendicular to the direction of pressure (pressing down on the stack of papers). This alignment of minerals into sheets is termed a foliation. Rocks that lack sheet-Ike minerals will not create a foliation_ Sandstone, composed mainly of quartz, is converted to quartzite, limestone to marble. Neither contains foliations.

Activity 1: Types of Metamorphism
Match the options for types of metamorphism would occur at each of the lettered locations in the image below:

QUESTION 25

Activity 2: Metamorphic Rock Identification
Use the information above, the Metamorphic Rock Identification Key in the Lab 4 Information Sheet, and the Rock Properties Slideshow to answer the following questions.

This rock has mineral grains of a size comparable to sandstone but as you look at the grains with a magnifying lens you see that their is no apparent cement and the grains are compressed together. There are no obvious planar features of this rock. This is called the (foliated, non-foliated) metamorphic rock. You apply HCI acid but the mineral in this rock does not react with the acid. You test the rock's hardness and find that the mineral it is made of is harder than glass and you cannot find any cleavage planes. The name of this rock is

QUESTION 26

This is a slate. It is a (foliated, non-foliated) metamorphic rock since it notably has a series of flat planes running through it. The rock has a slight sheen to it as you turn it in the light. The mineral grains in this rock are far to small to see so you reason that the parent rock from which this rock had metamorphosed was probably also very fine-grained, which could be (mudstone, sandstone, conclomerate).

QUESTION 27
Metamorphic Rock 3

This rock has a notable alternating pattern of light and dark coloration. While the planes are pretty wavy in this case, there are planes present running through this rock. The grains in the rock are fairly large and readily visible which leads you to think that the rock was produced by high-grade metamorphism (that is, the heat and pressure applied to form this rock was greater than that which formed other metamorphic rocks of lower grade). The name of this rock is

QUESTION 28

Metamorphic Rock 4

This rock is very shiny. It looks like it is mostly made of thin, platy minerals that you saw in the Minerals lab. The platy minerals are aligned such that there are clearly planes running through the rock. The fact that the mineral grains are quite large leads you to believe that this is a (low-grade, high-grade) metamorphic rock. This particular sample also contains visible garnets (this won't necessarily affect the name that you will call the rock but it is pretty neat nonetheless). The name of this rock is

QUESTION 29
Metamorphic Rock 5

This rock exhibits no planes running through it. It is composed of a series of interlocking grains that fit neatly against each other. You apply HCI acid to this rock and find that it fizzes when the acid comes in contact with it. The name of this rock is

QUESTION 30

Now let's revisit the rock cycle...
This is a photo of the Papakoloa Beach at Hawaii. It is also known as the green sand beach. This is because the beach sands are almost entirely composed of divine fragments (the image on the right shows a zoomed in picture of the sand grains).
Using the knowledge you learned from this lab, from previous labs, and from the information you are given (the bedrock composition, the texture of sediments... etc.), explain 3 things:
a. What is the source rock from which these green sands originate? How do you know?
b. I-low did these green sands form from the source rock?
c. Why is it unusual to see a beach made of green sand? (Think of how plate tectonics relates to this answer!)

QUESTION 31
You are now an expert of rocks!
Now let's practice thinking like a geologist!

Rebecca is a graduate student in Consciences. Her research project is about now climate and environment has changed over geologic time in southern Chile_ One day when she was working in the field, she came across a large outcrop (exposure of bedrock). She was super excited because this outcrop comprises a continuous sequence of multiple rock types, and she would be able to track every details of the earth's history recorded in the rocks.

She found that the bottom part of the outcrop is composed of very fine-grained mudrocks and she could find clamshells fossils in the rocks. As she move upward, she found that rock composition changes a lot. The top part of the outcrop is composed of sandstone and she could even find some broad-leaf leaf fossils in the rock.

After she came back from the field, she reviewed a lot of literature about this outcrop. She found that someone has reported the ages of the rocks. She learned that the bottom part of the outcrop is around 30 million years old. and the top part is around 25 million years old

How did the environment in which these rocks formed change from 30 million years ago to 25 million years ago? Using what you've learned for this lab, write a paragraph that tells a clear story of what happened, and explain your reasoning.

Attachment:- Geo sci lab.rar