Girl Scout Juniors Geology Activities
Do six activities from those listed on page 107-108 of your book. Selected activities are presented here.
1. Find out about the different types of training or education geologists need to do their jobs. Learn about other careers that relate to studies of the earth. You might arrange to have a professional in this field come and visit your group or you might visit a geologist to discuss his/her field of work.
Answer: A geologist obtains his/her training in a basic 4-year college science education. There are a certain number of required hours of college credit in geology courses, as well as english, mathematics, foreign language, physics, social studies, computers, and arts and humanities. This curriculum is intended to create a well-educated individual with a Bachelor of Science degree in Geology. Required courses in Geology include: general geology (including physical geology [general earth processes, like erosion, mountain-building, and deposition] and historical geology [geologic time as recorded in layered rocks]), geomorphology (land forms), sedimentology (processes of deposition of sediments), mineralogy (mineral identification and processes of formation), lithology (rock identification and processes of formation), optical mineralogy (optical properties of minerals), structural geology (rock structures and how to interpret them), hydrology (water movement, chemistry, and aquifers), economic geology (ore minerals and their occurrence), petroleum geology (the formation of petroleum and how to find it), marine geology (study of the processes that are active in the earth's ocean basins), geochemistry (chemical reactions and study of the formation of certain rock types), photogeology (study of aerial photographs and mapping), field geology (generally a field course in mapping techniques ending in completion of several mapping projects), and paleontology (the study of past life as recorded in sedimentary rocks).
With this background, the individual is a general geologist. This education is adequate if the geologist is to work as a geo-technician for engineering companies or in the service portion of the petroleum industry (mudlogging, etc.). A general geologist needs additional specialized training to obtain most geology-related jobs. This is obtained by going to college for an additional two years to study one or more of the above-mentioned fields to obtain a specialty or greater background in a specific geology-related area. A research paper (called a thesis) during the second year of graduate school is required to demonstrate the person's ability to develop a geologic project, carry on geologic investigations in a scientific manner, and write the results in a standard scientific format. Individuals with this degree of training are highly sought by both the petroleum and mining industries, and both state and federal government agencies.
Some individuals wish to continue their education and obtain a Doctorate of Geology degree. This involves an additional four years of research and study and the publication of a doctoral dissertation ñ an original research paper on some specialized area. Although having this education is great and it makes that person an expert, the individual is generally over-educated for most positions in industry or government. They may teach at universities (educating other geologists) or may work for specialized research centers. Many also open consulting businesses and work for the general public.
Other careers that may relate to geology include physics, environmental science, geography, mathematics, weather, chemistry, ecosystems, oceanography, astronomy, and biology. Have a geologist come and talk about what their particular work involves.
4. Start a rock collection. Go on an exploration hike to see how many different kinds of rocks or minerals you can find. Bring back a few specimens to examine in greater detail. Learn about the different classifications and groupings of rocks. Organize and label your rocks. Use reference books, museums, or the advise of another rock collector or geologist.
Answer: Many textbooks explain and show pictures about how minerals and rocks form. You can learn learn how to identify some of the more common rocks and minerals before you begin a rock collection. Get the following book from your school or community library:
Zim's Golden Nature Guide to Rocks and Minerals. It has brief and easy to understand information you will need to know before you begin a collection. I would also recommend you study about the geology of your area! This will give you an idea of what types of rocks you might find. The best way to do this is to get a local geologist to come and talk to your group about the local geology. Be certain to ask him/her to bring along some typical samples of what you might find locally.
Starting a rock collection is fun and educational! Rocks are all around us. Start by getting prepared. You need a permanent marker to number your samples, some ziplock plastic bags to put them in, and a pencil and notebook to write down a description of where you found them (back yard, creek bed, mountain side, driveway fill, road ditch), and other information like one-of-a-kind, typical sample, part of large mass, and so forth.
Don't forget a hammer as you might wish to break the sample to see what it looks like inside. A small magnifying glass is handy.
Once you have made your collection, then invite the geologist back to see and discuss what you found. Then you can organize and label your samples. Local rock collectors and hobbyists are great sources of information about where you can go to collect unusual specimens.
See also the links about Managing a Collection on the Rocks and Minerals page
5. Find out about one way in which fossils are made. Make a simulated fossil by pressing a leaf, rock, skeleton, bone, or dead insect into some soft plaster of Paris and allowing it to harden. This could also be done with some mud layered in a shallow box. Look carefully to see the details made in the impression when the item is removed.
Answer: You will be making an impression-type fossil in this exercise. I recommend using modeling clay rather than plaster of Paris or mud. It works much the same and is a lot less messy! See also Make Fossils
First, take a two-inch ball of single color clay and mash it out like a pancake. Leave it about 0.5-inches thick. Then use something smooth to remove your hand print, like a smooth piece of paper or cardboard or even a rolling pin. Place your item (try a feather, a coin, or a leaf) onto the clay and mash it into the clay with your cardboard or rolling pin. Then carefully lift the item from the clay. Observe the detail of your item left. The impression could be used as a mold to re-create the general shape, surface texture, and appearance of your item.
Think about if you saw this shape in a rock what it might mean. Let's take an animal for example. The animal is living on the ocean floor, then it dies for some reason and is covered with mud. After a long time, the mud turns to stone, let's say shale for this discussion. When the shale is broken just right, we see both the positive and negative impression of the original animal! We have the remains of a once-living organism that dates from the time when the sediment was deposited. The matrix that the fossil is preserved in tells us something about the sedimentary conditions during this time.
Which do you have in your clay example above, the positive or the negative impression? Correct, the negative because it is the imprint of the fossil, not the fossil itself. From looking at the impression left in the modeling clay, how much detail can you see in your ìfossilî? Use a magnifying glass. You should be able to see the surface texture and measure the size and shape, but we can not tell the color of the original plant or animal, nor can we tell anything about its internal makeup (like its internal arrangement of organs, fibers, etc.). So, imprints provide some knowledge of the original organism, but only to a limited degree.
7. To discover firsthand the effects of weathering on the land, do two of the following (I have listed three for you):
Go for a walk in your neighborhood and observe the chips, cracks, and rough areas in the sidewalk. Think about all the things that help make these happen. What natural processes are occurring that might have caused the changes in the sidewalk? Tell how the same natural processes that helped to crack the sidewalk will also help to disintegrate rock.
Constant natural processes appear to act slowly, but they are always present and available to act on rock. Let's consider your sidewalk. Did you see some cracks? In the neighborhood where I grew up we had some large trees that had pushed up the sidewalk in places due to the root growth of the trees. It was nearly impossible to skate across these areas of disturbed sidewalk. If you live in an area that gets lots of rain and freezing cold temperatures in the winter, then you may see cracks developed by a process called frost heaving. Ice forms in the ground as water freezes. Ice can lift concrete unevenly.
When this happens, the concrete may break due to the pressure caused by the lifting. If you live in a very dry climate, sometimes when you do have a rain, it causes flooding. Sidewalks can be washed away when water overflows from the street and manages to get under the edge of the concrete. Flowing water is tremendously powerful and can easily lift a section of concrete and move it. In a dry region, there may also not be much vegetation to hold the soil in place, so it may easily be washed away by flowing water.
If you live in the desert you may see cracks in concrete created from a different cause. Cold nighttime temperatures and hot daytime temperatures can cause concrete to shrink or expand. This can cause cracking. Did you ever wonder why you see a groove every few feet in a sidewalk? These are placed to control where concrete cracks due to shrinkage and expansion. Some recent concrete sidewalk construction even has boards or sawn grooves between sections for this same purpose.
Discover what happens when water gets into cracks and spaces in rocks and then freezes. Fill a small enclosed plastic container with water and then freeze it. What happens to the container? What does this mean for areas where there is water that freezes?
I did an experiment similar to this when I was young, but I used a small mayonnaise jar that I put in the freezer section of our refrigerator! My mom was quite upset when she found the broken glass jar in her freezer! If I had just put the jar in a ziplock baggie, I would not have gotten into trouble. So, I suggest you use a small plastic container with a screw-cap type lid. It may not break, but it will expand noticeably. You might even want to try this with a balloon full of water! Anyone familiar with the old plastic ice cube trays knows that the water is level when you put it in the freezer but the ice cubes are rounded when you remove them. This shows the amount of expansion.
Water has the uncommon property of expanding as it freezes. When in a confined space, like a jar or in a small crack or hole in the ground, freezing water can create a tremendous force. Such forces work to lift or loosen rock in the ground, or move rock near a cliff or bluff face so that gravity (gravity is a constant force pulling everything toward the center of the earth) can assist in causing a rock fall.
Have you ever seen the effects of a landslide? Both water and gravity play important roles in this geologic event. By freezing, water may either cause fractures to form or cause the enlargement of existing fractures in a rock or soil mass. Fractures may then be lubricated by water from rainfall. When the mass of rock becomes unstable, gravity pulls it downhill. Geologists call this process mass wasting. This process is especially active in areas with steep slopes, bluffs or cliffs, and along highways where some of the rock or soil has been removed during road construction. Have you ever seen a sign along a road that says Caution - Falling Rock? If you have, you were in an area where the rock may be unstable due to excavation and the active forces of water and gravity.
Visit a cemetery and look at the effect of water and wind on the different types of headstones. Do some types of stone last longer than others? Can you discover why?
When visiting a cemetery to examine the weathering of headstones, ask that the Cemetery Supervisor or head maintenance man accompany you. This person should be able to help you do two things: identify the types of stone used in headstones and show you some different stones that were all erected about the same time (within a few years of each other). Ask to see some of the oldest stones in the cemetery and to see some recent ones. A precaution: please be respectful of grave sites as this is the final resting place for human remains, who were at one time, just like you and me.
You should find three basic types of headstones: those composed of igneous rock types, those of gneiss, and those of marble. The igneous rock types may have a variety of crystalline textures, varying from medium- to coarse-grained, and colors that may range from black, dark red, pink, and mottled gray to cream. The minerals will be uniformly distributed in the rock. Igneous rocks all take and generally hold a high polish for a long exposure to weather. Gneiss, a metamorphic rock, will exhibit some light and dark banding of the minerals composing the rock. It polishes well and also stands up to weathering. Marble is a metamorphosed limestone and may be composed of either the minerals dolomite or calcite (or both). It is generally a light-cream to white color and may have streaks of pastel green or pink in it. Marble used for headstones takes a medium polish and is usually medium- to coarse-grained. The minerals that compose marble are reactive to acids.
What did you find out? Some cemetery stones in my area are in such bad condition that the engraved lettering is no longer visible. What type of stone commonly shows the effect of weathering? Was it marble or limestone? How did this happen?
Well, what is the most common source of acid in the natural environment? Isn't it rainwater? Rainwater is naturally acid because it dissolves carbon dioxide from the air as it falls to the ground. Given many years, this weak acid (called carbonic acid) slowly dissolves away the headstones composed of limestone and marble. The acid condition of natural rainwater causes little reaction with the minerals present in granites and gneiss (feldspar, quartz, mica). So in this instance, we have discovered that the chemistry of the water can cause weathering due to the chemical reaction of certain minerals in the rock, not just by the mechanical movement of water or forces created by it when it freezes and expands.
8. Find out what makes up soil. Collect two cups of soil from a site of your choice. Spread it out on a light colored sheet of paper. Using a stick to help separate the contents and a magnifying glass to get a closer look at the particles, separate the various particles into groups. Make a list of the different particles you have found. Discuss with your group what you have found, what might grow in the soil, where the things in the soil may have come from, and how soils in other areas may be different.
Answer: You should try and do this exercise with soils from two different areas so you have different types of soil to observe. Just get two girls that live in different areas to get some soil from their own backyard for this project. Use a large styrofoam cup to put the soil sample in. Collect your soil sample by taking a small shovel and cutting into the soil, then take a dinner knife and cut out a sample so you retain the vertical profile of the soil. Be certain to take from the roots down to about 4 or 5 inches. Try not to mix up the different layers, but place the sample in the cup like you were taking a core sample or plug of soil. We are interested in not just the soil composition but its different layers.
The upper most part of your sample should be somewhat darker in color and when you pull it apart there should be lots of organic matter, like grass roots, decaying vegetation, and seeds. These materials put nitrogen and other nutriments used by plants back into the soil when they decay. There will be some mineral matter also, along with possibly some bugs or dead bugs, worms, and other small animals. If you got a sample that was deep enough, you will have lesser amounts of roots and lesser amounts of traces of animals. There will be more mineral matter and you may be able to see clay, sand, or even gravel particles.
You may have a very deep soil and only get a sample of the upper soil horizon. I suggest you find a soil scientist or specialist to visit your group when you do this exercise. A specialist can teach you what you need to know about soils and how they are classified. Some soil specialists go to college to get a degree in Soil Science offered by college agriculture or agronomy departments.
As to where soils come from, there are two basic types: those that formed in place from the underlying rock and those that were transported to their present position by wind or water. Soils form by the incorporation of humus (derived from the decay of plants and animals) into the upper layer of mineral matter on the earth's surface. This happens as vegetation begins to establish itself on bare ground. If the process is carried to completion, then the existing soil reflects the conditions under which it formed. There are many different types of soils: those that form in the desert, in the tundra, in tropical rain forests, in temperate climates. With the differing climate conditions, the underlying rock reacts differently to produce different types of soils. If the soils are transported types, washed in by flooding or blown in by the wind, then they result in differing types of soils depending on the climate where they are deposited. Soils vary in thickness from almost non-existent to over 30 feet.
10. Find out how water carries things and when it leaves them behind. Do at least two of the following (I picked the following two to do because not everyone lives near a lake or ocean, or has a microscope available to them):
Shake up a jar of water with some gravel, sand, silt, and/or clay inside. When you stop, watch which settles first and how layers of sediment form.
What is happening here? The coarser particles are on the bottom and the sediment generally gets finer grained as you go up in the layers. If you had some clay in the jar, the water will remain muddy for a long time after you have set it down. Why is this happening?
The energy it takes to keep particles suspended (floating) in water is related to both the size and the specific gravity (a measure of how dense the particle is relative to water) of the particles. Let's assume that all the particles are the same mineral, say quartz.
In this case, the specific gravity is the same. As the energy of the moving water begins to decrease, the largest quartz grains drop out first, then the medium sized ones, and finally the smallest sized ones. So you have a stratigraphic sequence of coarse, medium, and fine as you look from the bottom to the top of the layers. If you had some particularly heavy mineral in the sample, like gold perhaps, you might see something a little different happening. Gold is very dense compared to quartz and water so it has a high specific gravity. If there was some medium- to fine-grained gold in the jar with the other materials and you shook the jar up, the gold would drop out with the coarser grained quartz particles because the energy would not be enough to keep it in suspension. We would find the gold in the lower one-half of the sediments in the jar.
A fun experiment is to get some construction sand. It is mostly composed of medium-grained quartz sand. Then get some iron filings about the same size as the sand and mix them with the sand in the jar. Now fill the jar with water and shake. Set on a table and look at what happened. The iron filings have higher specific gravity even though they are about the same size, so they settle to the bottom of the jar first. They drop out first because the energy of the moving water was not enough to keep them floating.
Now we can begin to think about how layers of sediment form. Where does sediment come from? From the breakdown of rocks. Erosion by wind or moving water transports the sediment until it is dropped due to a loss of energy. Moving water and even wind sort out the various sized particles and moves them to another location. Let's think about a beach. There are several kinds of beaches. Rocky beaches have so much wave energy that they are washed free of all small particles like sand and clay. They may consist of rocky outcrops or have gravel or cobble layers. Sandy beaches are present on many coastlines. Where does sand come from? It is normally transported to the coastline by rivers and then transported along the ocean-land contact by currents in a process geologists call ìlong shore drift.î What happens to the mud that rivers transport? Often it is carried a long distance from shore by the river's current before it begins to settle out.
Mud is mostly composed of fine-grained sediments, like clay. Clay will stay floating in the water a long time before it finally settles to the bottom. So we have a water-based system that transports and sorts sedimentary particles based on their size and density.
Wind transported sediments also are sorted during movement. Sand dunes contain very little clay. Transportation by the wind is a winnowing type of process that removes only the finer particles (sand and clay) from a source area, then deposits them somewhere else. Sand-sized particles drop out first and the clay is carried on, eventually to be deposited as dust. In some places on our globe, large sand-dune regions exist. In other areas we might find dust deposits as thick as 300 feet; brought in by the wind. So, a wind-based process sorts particles depending on the amount of energy it takes to lift and float the grains.
Watch how water drains from various surfaces after a heavy rainfall. How does water change things?
This might be hard to do if you live in a desert area.Let's consider several types of surfaces that rain may fall on, starting with a street/parking lot. A street/parking lot cannot absorb any water that falls on it because it is covered with concrete or asphalt. If it has a slope (is tilted so the water will drain), then the water runs off rather quickly, usually to a drain system. What happens when the same amount of rain falls on a grassy yard? Up to a point the grass holds back the flow of water and allows some of it to soak into the ground. If it is too heavy a rainfall in a short time, then the water may flow rapidly off the grass and into the street or some other drained system. If this same amount of rain falls on a section of forested land, the trees and leaf litter break up the water's energy and much of the water soaks into the ground. Some runoff will still flow into creeks, streams and rivers, but the water in these drainage systems tend to be relatively clear because not much sediment is removed from the land.
Now, take the same area that is bare ground and let it be rained on. What happens? Nothing is there to prevent the energy of the falling raindrops from beating on the soil. Nothing is present to hold back the flow of water across the slope, so by the process of erosion the water carries off the top layers of soil. Creeks, streams, and rivers that drain such areas are muddy because they are transporting particles of soil. So water can dramatically change the land by erosion when there is no plant cover to slow down and break up the energy of the water.
Here's a little experiment you can do to demonstrate what happens with erosion. You will want to do this outside because it could make a mess! You need some soil from your yard. Fill a flat container level to the top with the bare soil. A flat cardboard box lined with aluminum foil is good. Make another one of these containers, but put some grass sod on the top so the root line is level with the top of the box. It's like having two planter boxes, one full of dirt with no vegetation and the other full of dirt with vegetation.
Now take a gallon plastic milk jug and fill it with water. Place both boxes of soil on a slight slope (one side about 1 inch higher than the other). Note: when you pour the water from the milk jug, turn the jug upside down quickly so the water rapidly flows out! Now, pour the milk jug full of water into the upper end of the grassy box first. What happens?
Some water may reach the other side of the box and flow out. Is it fairly clear or muddy? Now refill the milk jug and pour it into the upper edge of the dirt-only box. What happened? If some water reached the other side of the box and flowed out, was it clear or muddy? You should find that water draining from vegetated ground remains clear because the vegetation (grass and its roots in this case) help hold the soil in place. The upper end of the dirt-only box will show signs of erosion and a fair amount of soil and dirt may have washed out of the box.
Farmers practice the best methods of farming to prevent soil loss by wind or water. They try to control erosion by contour plowing, leveling certain fields for crops, and leaving areas of vegetation around fields to stop the rapid runoff of water. When possible they leave dead vegetation standing in the field to help prevent erosion Non-till planting is becoming important in some farming regions. I suggest you visit a local farm and talk to the farmer/farm manager about what he/she does to prevent soil erosion. You might also get some pamphlets from your local Cooperative Extension Agency about soil erosion and how to prevent it.
Have any photos from your geology activities? Please share with us!