Introduction
Most middle school students are not familiar with the geology of Connecticut. This unit will introduce students to the geology of Connecticut through its history, rocks, soil, and the minerals that are contained in the rocks.
The purpose of the unit is to give the student some of the history of Connecticut landforms, rocks, minerals and to show how these were formed and how all this came about. Also, it is intended to give students hands on experience with geological materials and to describe a unique cultural landscape which has played an important role in the development of Connecticut which, still is an important visual element in maintaining Connecticut’s environmental character.
GOAL
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1. To provide experience with soils, rocks and their minerals through hands-on materials within the classroom.
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2. To provide basic data through geologic mapping and research for use in science and math.
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3. Familiarize the student with the fundamentals of geological language and usage.
OBJECTIVE
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1. Field trips—East Rock Park and a quarry.
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2. The students will be able to identify rocks and soils and to read charts and maps.
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3. Students will be able to solve math problems.
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4. They will be able to write simple math problems using a simple four-step plan and solve them.
FOUR STEP PLAN
To make batons for relay events we cut a rod 2.28m into 8 equal pieces. How long is each piece?
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1. Understand the
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What do you know?
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2.28m
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problem?
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What do you want to know?
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2. Make a plan.
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What do you do to
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Divide 2.28 by 8
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solve the problem?
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3. Do the
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Show your work.
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0.285
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arithmetic.
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8) 2.28
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4. Give the
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How long is each
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0.285m
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answer
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piece?
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or 28.5cm
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Connecticut Land Surface
Connecticut was once a rugged land, shaped by violent forces in the earth and by the sea. It was carved by glaciers that left a heritage of rolling land, rivers, lakes, hills, and valleys.
The general shape of the land surface was developed by erosion over tens of millions of years before the ice age. The principal rivers were established then, though they were often altered by glaciation. Erosion is the process that moves rock and soil particles on the earth surface from one place to another. It can be caused by running water, glacial ice, waves and wind. The ice age began about two million years ago. The most recent Ice Age began about 100,000 years ago and ended about 15,000 years ago.
The present land surface is due to the ice age. Thousands of years ago when the climate was much colder an ice sheet known as a glacier was formed. All of Connecticut was covered with ice. This ice moved slowly, coming southward over the hills, mountains and rocks in its pathway. Some rocks were frozen into the ice at its lowest level and it acted like a piece of sandpaper, smoothing down the rocky surface. Although, the valleys and hills were here before the glacier, changes in the surface of Connecticut were made.
After the summers became warmer the glacier was five hundred to eight hundred feet thick over the southern part of Connecticut and much thicker further north. The melting of this ice produced great rivers of water, carving deeper valleys and carried large quantities of clay and sand down to the sea. The larger rocks that the glacier had picked up and carried were dropped directly on the ground. After the ice sheet finally melted, the land lay bare of all vegetation. It was a great rocky muddy region in the summer—but the climate was cold most of the year. Vegetation established itself quickly after the ice left.
There are four present land forms in Connecticut. There is a low coastal strip which extends along the sea coast from New York to Rhode Island. It is the old rocky surface broken by small rivers and three large ones that have carved out valleys which reach the Sound. On the west the land is made up of many small hills and valleys that rises to a point of 2,315 feet in the northwest corner of the state. The Central Valley is quite low and it is about a hundred feet above sea level on the Connecticut River near Massachusetts. The valley has a number of trap rock ridges and most of the other rocks are sandstone and shales.
East of the Central Valley is the Eastern Upland which is a hilly region cut by many river valleys. The Western Upland is much higher than the eastern uplands. (See Appendix A) Connecticut land is about one hundred miles east and west along the sound and fifty miles north to the Massachusetts line. Its area is 5,004 square miles counting the lakes.
There are major forces that created landforms. They are the ice riding over the hills, the volcanic eruption that gave Connecticut the trap rock and the rivers that leveled the mountains causing landforms. Many years ago landforms were quite different in Connecticut from what they are today. Over the years several forces have shaped what we see today. Some of Connecticut landforms rose to thousands of feet. Weather conditions produce brooks and rivers; flowing water which has a lot of power, wore away the surface. The material worn off the mountains was deposited in valleys and became soil.
SOIL
Soil is not just dirt. It is a combination of tiny rock fragments; water, air, dead vegetable particles, tiny living plants and animals. There are four different kinds of soils found in the state. These soils differ because they have been produced on different kinds of glacial deposits.
Glaciers are not the only agents that move parent materials about from their place of origin. Others, such as gravity, water, and wind, are also important in moving rock material about. These agents may move the parent material of soil many times. Each time this occurs the rock particles may be further broken down and sorted as to size.
Each agent distributes soil making materials in a characteristic manner. The geological classification of these materials that give rise to our Connecticut soil is made as follows:
TILL OR GLACIAL TILL
. This is a mixture of rocky material. It contains varying amounts of gravel, sand, silt and clay that was deposited by the ice with little or no water transportation.
STRATIFIED DRIFT
. This rock material is sorted by waters from glaciers and left in layers as partially sorted gravel. The finer silt and clay particles generally were carried off and deposited separately.
ALLUVIUM
. These materials are moved by water and later deposited along stream banks. These alluvial deposits form the terraces found along many streams and rivers.
LOESS
. This deposit is relatively uniform, fine material, mostly silt. It was presumably transported by wind during dry weather periods right after the melting of glacial ice.
GLACIOLACUSTRINE
. These are very fine sands, silts, and clays picked up by glacial action, carried in the melting ice water and deposited in glacial lakes. In some instances the deposited material looks like a layered cake. The layers vary in thickness.
ORGANIC DEPOSITS
. These plant materials are accumulated in shallow water. As successive generations of plants died, the residues gradually filled the shallow, saucer-like depressions. The deposits are identified as either peat or muck. Plant material that can still be identified is regarded as peat. Organic accumulations that have decomposed so as to make identification of the plant material impossible are called muck.
COLOR
. The color of soil is its most obvious characteristic. Along with structure and texture, color forms the basis for distinguishing the various soil horizons.
Many soils are red and yellow in color. Their color is directly related to the presence of several iron and manganese compounds. For example, if a soil is derived from parent material rich in iron minerals, it is generally highly colored, with the exact color depending on the mineral form of the iron. The mineral form is dependent on oxygen supply. Red color in a soil usually indicates good drainage and good aeration, especially in the lower horizons. Our red Connecticut Valley soils are derived from sandstone parent materials high in iron content.
Gray and whitish colors in soil are caused by several substances. These are mainly quartz, kaolin and other clay minerals, and carbonates of lime and magnesium. The gray or blue-gray soils of poor drainage and low aeration owe their color to iron in the reduced form. Low amounts soft organic matter and concentrations of reduced iron are the basis of the gray colors of some Connecticut soils.
TEXTURE
. Soil texture refers to its coarseness or fineness. It is determined by the proportions of individual soil grains or particles.
Soil particles are classified by size into groups called “soil separates.” These are sand, silt, and clay.
The proportions of these particles of different sizes determine soil textural classes such as sand, loamy sand, clay loam, silt loam and others. Textural determinations are generally made within the surface layer or topsoil, and any reference to texture is understood to be that of topsoil. Some aspects of particle size are indicated below:
SAND.
Sand serves as a framework for the chemically active part of the soil, such as clay. Sand particles feel gritty when rubbed between the fingers. Sand is usually single grained, and, unless coated by silt or clay, shows practically no stickiness when wet. The sand particles are larger than those of silt and clay, with diameters from 0.05 to 2.0 millimeters.
The water-holding capacity of sand is low. This is due to large pore space between particles which allows water to drain readily from the soil. Soils with large amounts of sand possess good drainage and aeration, and are usually referred to as “light soils” or “coarse soil.”
SILT
. Silt particles vary from 0.002 to 0.05 millimeters in diameter. These are so small that it is hard to identify single particles with the naked eye. The coarser silt particles are similar to the fine sands in shape. However, the former have a greater surface area of exposure than does sand. Like sand, silt takes little part in the chemical process of the soil.
Soils
in which silt predominates have a fine texture, and water movement through the soil is slow. Soils high in silt are hard to work and are referred to as “heavy soils.”
CLAY
. The finest of soil particles is clay. These are smaller than 0.002 millimeters in diameter. Clay is also the most chemically active soil separate.
The sediments deposited in the lakes that used to fill the valleys may be either sand and gravel, or clay. Soil that is developed on clay is wet because water doesn’t pass through it easily. This soil is wet and sticky. The second soil which is developed in sands and gravels is dry soil. The rain passes through it easily and it is light and good for farming root crops. The third type of soil is formed on till. Till is a mixture of large and small particles that the glacier dropped helter-skelter on the ground as it melted. This soil falls between extremes of wetness and dryness that the clay and sandy soils represent. It holds enough water for crops. The main disadvantage to this soil is the number for rocks in it. The fourth type of soil is alluvial soil deposited by rivers. It is deposited by sedimentary materials and it is a mixture of sand and clay particles of various sizes.
SAMPLE LESSON PLANS
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Activity
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Materials
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Soil Samples
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Paper
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Toothpick
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Magnifying Lens
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Pencil and Paper
In this activity students are going to take a close look at samples of soils to see what it is made of.
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A. Obtain the above material
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B. Place one or two spoonfuls of soil on the paper
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C. Use the toothpick to separate the soil into many different materials: Eq. light grains, dark grains and soft materials. Put similar materials together. On a sheet of paper make a table and label each sample.
(figure available in print form)
