Term 4 Science
How the earth changes
- Start a discussion: Is soil an important ingredient in your everyday life?
- Discuss with your children that last night you slept on a building built on soil. You breathe air from plants that come from the soil. You wear clothes made from plants that grow in the soil. We build on soil. We play on soil. We drive on soil. The entire Earth is dependent on soil.
- Ask your students what they think soil actually is.
- Allow students to discuss with a partner what they think is in soil.
- Explain that soil is made up of rock, sand, clay, silt, air, water and organic matter (dead plants and animals).
- Show the images of soil and have students identify what they can see.
- Explain to your students that today they will pretend to be a Geologist.
- Ask “What is a Geologist?” A geologist is a scientist that studies the surface of the Earth and what it is made of. This branch of science is called geology, which means the study of rocks. If you like digging in the dirt, then this may be the job for you! A geologist is a scientists who studies rocks,
- Draw out that it is someone who studies things on the Earth.
- Provide students with 2 different samples of soil. You can use beach soil and garden soil.
- Set students to task on the Geologist Soil Discovery Activity Sheet.
The first three pictures are of the same rock, just in different time periods. Pay attention to the dates under the pictures and see what the water did to this rock.
1890
1910
1920
1970
1.Have students create a table in word on their MacBooks and complete a TWLH chart. "We use a TWLH chart to show our thoughts and ideas about a topic before, during and after an investigation."
A TWLH chart includes four sections with the headings:
What we think we know, What we want to learn, What we learned, and How we know.
Complete column one: Invite students to contribute ideas about soils, rocks and landscapes and how they change over time.
Complete column two: ask students to suggest questions they have about soils, rocks, landscapes and how they change.
Discuss words that students know about soils, rocks and landscapes and how they change on a word wall. Group words for display.
Erosion video - Bill Nye http://www.youtube.com/watch?v=lsjsdc7I4FE
A TWLH chart includes four sections with the headings:
What we think we know, What we want to learn, What we learned, and How we know.
Complete column one: Invite students to contribute ideas about soils, rocks and landscapes and how they change over time.
Complete column two: ask students to suggest questions they have about soils, rocks, landscapes and how they change.
Discuss words that students know about soils, rocks and landscapes and how they change on a word wall. Group words for display.
Erosion video - Bill Nye http://www.youtube.com/watch?v=lsjsdc7I4FE
The Earth's surface
The outer crust of the Earth is made up of rock. In places the rock is covered by soil or water. This outer shell isn’t rigid and events, such as earthquakes and volcanos help shape the landscape as they impact on the rocky layer and bring new material to the surface.
The word ‘rock’ in common usage can refer to large cliffs and boulders as well as to small stones or pebbles. Scientists are more precise when they use the word ‘rock’ and understand it to mean an aggregate of minerals.
Geologists (scientists who study the origin, history and structure of the earth) classify rocks into three basic types depending on the way that they were formed: igneous, sedimentary and metamorphic. Igneous rocks are formed from the solidification of the minerals found in magma.
Sedimentary rocks are formed at the Earth’s surface from the accumulation and consolidation of sediment. Metamorphic rocks are formed from pre-existing rocks within the Earth’s crust by changes in temperature, pressure and by chemical action.
The word ‘rock’ in common usage can refer to large cliffs and boulders as well as to small stones or pebbles. Scientists are more precise when they use the word ‘rock’ and understand it to mean an aggregate of minerals.
Geologists (scientists who study the origin, history and structure of the earth) classify rocks into three basic types depending on the way that they were formed: igneous, sedimentary and metamorphic. Igneous rocks are formed from the solidification of the minerals found in magma.
Sedimentary rocks are formed at the Earth’s surface from the accumulation and consolidation of sediment. Metamorphic rocks are formed from pre-existing rocks within the Earth’s crust by changes in temperature, pressure and by chemical action.
Volcanic rock is formed when the molten minerals (magma) inside the Earth arrive at the surface, for example, through volcanic activity or sea rifts. Not all magma is extruded at the surface, some remains beneath the surface as intrusions into surrounding rock where it can cool. At the Earth’s surface magma becomes lava. As it cools, the minerals change from liquid to solid and form igneous rocks. The nature of the materials formed depends on the rate of cooling. If lava has a long time to cool, then individual minerals separate as distinct crystals to produce, for example, basalt with many different grains of crystals. However, if the same lava cools quickly, the molten mineral mix will harden and form a glassy black rock called obsidian. If it cools quickly and captures air pockets, a light crumbly stone called pumice is created; this is not dense and floats on water. All these rocks will have the mineral composition of the lava that created them, which might also be specific to different regions.
Sedimentary rocks are the most common type covering approximately 75% of the surface of the continents. Some examples are: sandstone, siltstone, shale, limestone, chalk, gypsum and coal. Their formation involves weathering of pre-existing rock, transportation of the material away from the original site (erosion) and depositing the eroded material in the sea or in some other sedimentary environment. Sedimentary rocks typically occur in layers or strata that cover large parts of the continents. The Grand Canyon in the US is a good example of sedimentary rock strata. Sedimentary rocks are formed from sediments that have been compacted and cemented to form solid rock bodies.
Metamorphic rocks are formed from rocks that have been altered by heat, pressure and chemical action to such an extent that the diagnostic features of the original rocks are modified or obliterated. Some examples of metamorphic rocks include slate, quartzite and marble.Rocks are made up of a variety of minerals put together in different ways resulting in different colours and textures. Geologists classify rocks based on their texture and composition. The texture of a rock refers to the size, shape and arrangement of the constituent mineral grains, whilst the composition of a rock is based on the chemical composition of the minerals it contains. Minerals have physical properties, such as cleavage, hardness, specific gravity, colour and streak (the colour of the powdered mineral).
Changes to the Earth's surface
Weathering and erosion video
http://studyjams.scholastic.com/studyjams/jams/science/rocks-minerals-landforms/weathering-and-erosion.htm
The surface of the earth is constantly changing. Land is being uplifted through processes such as plate tectonics and volcanic activity. Landforms are then further shaped through the processes of weathering and erosion. Weathering is the process by which rocks are chemically altered or physically broken into fragments and involves little or no transportation of the fragments. Rocks can be weathered, for example by ice formation in rock cavities which breaks the rock apart, and changes in temperature causing rocks to expand and contract which fractures it. (Scientists understand rock to mean an aggregate of minerals and classify rocks into three basic types depending on the way they were formed: igneous, sedimentary and metamorphic).
Rocks can also be weathered through chemical processes, for example, the mild acidity of some rainfall can cause minerals in the rocks to slowly dissolve. This is how caves such as the Jenolan Caves in New South Wales were formed. Acid can also be released from living things, for example, the decay of organic material, or by direct secretion of acids (lichens).
The rate at which weathering occurs depends on three main factors: climate, the susceptibility of minerals to weathering and the amount of surface exposed to the atmosphere. The Devils Marbles in the Northern Territory are an example of rock bodies modified by weathering.
Erosion
Erosion is the process that loosens sediments and moves them from one place to another. Agents of erosion include:
WATER
ICE
WIND and
GRAVITY.
Erosion is affected by variations in the Earth's surface. For example, if a creek flows over a cliff, a deep pool often forms at its base because the impact of the water falling from a height causes more erosion. Once there is mild erosion, subsequent water tends to flow in the same place, creating deeper and deeper river beds.
WATER
ICE
WIND and
GRAVITY.
Erosion is affected by variations in the Earth's surface. For example, if a creek flows over a cliff, a deep pool often forms at its base because the impact of the water falling from a height causes more erosion. Once there is mild erosion, subsequent water tends to flow in the same place, creating deeper and deeper river beds.
Human activity can also lead to erosion, for example, the removal of vegetation and contractions such as fences or dams affect erosion rates.
Trees bind soil with their roots, slowing erosion, but their roots can also assist to break up rocks. The decay of once-living things (organic matter) can cause water to become more acidic, inducing chemical weathering of rocks. Rainfall and wind corridors are in turn influenced by the landscape.
By clearing plants away and leaving soil bare after harvest, farmers can leave soils vulnerable to erosion. The top layer of the soil is the most susceptible to being blown away. This is also the richest source of nutrients for crops that farmers grow.
Time scale of change
Many rocks take a long time to be broken down and worn away in natural conditions. However some rocks can be weathered very quickly once they have been exposed. For example, the limestone of the Twelve Apostles formation in Victoria developed around 20 million years ago on land. Between 7 000 and 10 000 years ago, at the end of the last ice age, sea levels rose and limestone was exposed to the sea. Since the force of the waves has slowly weathered and eroded the cliffs to create isolated stacks of rocks. In 2005, one of the stacks collapsed, leaving eight standing. The rate of erosion at the base of the limestone stacks is approximately 2cm per year. Due to wave action eroding the cliff face, existing headlands are expected to become new limestone stacks in the future.
The creation of soils can take hundreds of years; however the erosion of soils can happen very quickly. For example, a mound of loose soil on a hill can be destabilised by water or by vibrations from an earthquake. the hillside might then suddenly collapse due to gravity. the presence of plants such as trees provides a buffer against wind, and all plant roots can help bind soil, reducing the amount
Australian Soil
Most of Austalia's landmass is away from tectonic plate margins and has been exposed above sea level for a very long time. This has allowed weathering to occur over a long period. Long term stability, and a relatively dry climate, ensured that soil producing activity was very slow. Austalian soils are very old, nutrient poor and slow forming, and need to be protected from loss by erosion.
Australia is the flattest continent, with few high mountains, as well as the lowest, with a mean elevation of 300 m, compared with the world’s mean of 700 m. Low relief contributes to low rainfall. There is little water available for weathering of rocks, and for transporting weathered material. This means that there has been little renewal of soils across most of the continent for millennia. In much of Australia, the vegetation cover is sparse, contributing to a slow rate of soil formation. Arid climate also results in lower levels of organic matter being available to enrich soils. This means Australian soils are generally very old, nutrient poor and slow forming, and need to be protected from loss by erosion.
Australia is the flattest continent, with few high mountains, as well as the lowest, with a mean elevation of 300 m, compared with the world’s mean of 700 m. Low relief contributes to low rainfall. There is little water available for weathering of rocks, and for transporting weathered material. This means that there has been little renewal of soils across most of the continent for millennia. In much of Australia, the vegetation cover is sparse, contributing to a slow rate of soil formation. Arid climate also results in lower levels of organic matter being available to enrich soils. This means Australian soils are generally very old, nutrient poor and slow forming, and need to be protected from loss by erosion.
http://scienceweb.asta.edu.au/years-3-4/unit3/lesson-one/yr34-unit3-lesson-one.html
Rock/erosion experiement
SOILS
There are many different classifications of soil. Scientists classify scientists based on how a soil is used. For example, by farmers to grow crops.
Water is an integral part of soils. A dry soil contains water but it is not available for plants to use.
Although soil is not nutritious for mammals, other organisms such as bacteria, fungi and earth worms digest its organic matter as a source of energy.
Soils have have different properties:
Soil experiment
1. Look at the soil through the clear plastic cup and describe the characteristics such as colours and layers.
2. Spread the soil on a piece of paper and look for details such as types of particles and leaves.
3. Use the magnifying glass to look at particles closely.
4. Rub the soil between fingers to feel its consistency.
5. Listen as the soil is rubbed on the paper.
6. Add 1 cup (250ml) of water to your jar of soil and shake well.
7. Record what you see: Features of soil samples.
Discussion Questions
Rock/erosion experiement
SOILS
There are many different classifications of soil. Scientists classify scientists based on how a soil is used. For example, by farmers to grow crops.
Water is an integral part of soils. A dry soil contains water but it is not available for plants to use.
Although soil is not nutritious for mammals, other organisms such as bacteria, fungi and earth worms digest its organic matter as a source of energy.
Soils have have different properties:
- Permeability (the rate at which water moves through the soil)
- Water holding capacity
- Porosity (amount of small spaces)
- pH (a measure of the acidity or alkalinity)
- Colour
- Texture (If a soil feels gritty, this indicated the presence of sand, whilst a silky feeling has clay or silt)
Soil experiment
1. Look at the soil through the clear plastic cup and describe the characteristics such as colours and layers.
2. Spread the soil on a piece of paper and look for details such as types of particles and leaves.
3. Use the magnifying glass to look at particles closely.
4. Rub the soil between fingers to feel its consistency.
5. Listen as the soil is rubbed on the paper.
6. Add 1 cup (250ml) of water to your jar of soil and shake well.
7. Record what you see: Features of soil samples.
Discussion Questions
- What did you notice?
- In what ways were the soils similar?
- In what way were the soils different?
- Can you think of other soils that are different from these?
- Why do you think scientists want to know about different types of soils?
Soil is composed of small particles of rocks and minerals, plus varying amounts of organic material (derived from living things), water and air. The particles are of different sizes ranging from sand to silt to clay. Sand makes a soil feel gritty; silts are similar to clays but have slightly larger particles; and clay feels silky to the touch because it has the smallest particles. The mixture of these particles gives soil its texture which influences how much water a soil can hold. Generally, the smaller the soil particles (the more silt and clay), the more water a soil can hold. Soil scientists use texture to classify soils, such as sand, loamy sand, loam, clayey sand and medium clay. The ideal soil texture for growing plants is loam, a mixture of clay, silt and sand. Soil composition is different in different places. These differences can be seen in a very small distance, such as from one side of a garden or farm to the other, as well as from country to country. The differences depend on the type of rocky material the soil was made from and the kinds of organisms that live in, around and on the soil.
Colour is a simple method of classifying soil. Black or dark brown soil is generally fertile soil for growing plants. Plain brown or yellow soil often indicates that the level of nutrients and organic matter is low and the fertility of this soil is low. Pale soils need plenty of organic material and mulching to become fertile. Red soil usually indicates extensive weathering and good drainage, but often it needs nutrients and organic matter to be fertile. The red colour is due to the oxidising of iron compounds (‘rusting’) in the soil. Organic material that can still be decomposed is called compost, whereas organic material that is stable is called humus (a Latin word meaning earth or ground).
Rocks
A rock is made of mineral materials in a solid state. Visit this page to see different specimens of rocks: http://www.rockhoundkids.com/2gallery.htm
A rock is made of mineral materials in a solid state. Visit this page to see different specimens of rocks: http://www.rockhoundkids.com/2gallery.htm
Geologists use features such as the mineral composition, the shape, size and orientation of the fragments in the rock to classify rocks according to their origin.
Properties include:
Use a magnifying lgass to examine the rock.
Describe what you see - colour, shape, size.
Properties include:
- Density (the ratio of mass to volume. A rock that floats in water - pumice, is less dense than water).
- Hardness (resistant to shape change when a force is applied).
Geologists are scientists that study rocks.
- work in a number of areas such as mining or on building development projects
- conduct field studies and collect samples such as rocks and fossils
- study landforms such as mountains to determine how they were formed
- study local areas to determine their history
- study rocks to determine how they age.
Types of rocks
Sedimentary
Sedimentary rocks are formed from particles of sand, shells, pebbles, and other fragments of material. Together, all these particles are called sediment. Gradually, the sediment accumulates in layers and over a long period of time hardens into rock. Generally, sedimentary rock is fairly soft and may break apart or crumble easily. You can often see sand, pebbles, or stones in the rock, and it is usually the only type that contains fossils.
Examples of this rock type include conglomerate and limestone.
Metamorphic
Metamorphic rocks are formed under the surface of the earth from the metamorphosis (change) that occurs due to intense heat and pressure (squeezing). The rocks that result from these processes often have ribbonlike layers and may have shiny crystals, formed by minerals growing slowly over time, on their surface.
Examples of this rock type include gneiss and marble.
Igneous
Igneous rocks are formed when magma (molten rock deep within the earth) cools and hardens. Sometimes the magma cools inside the earth, and other times it erupts onto the surface from volcanoes (in this case, it is called lava). When lava cools very quickly, no crystals form and the rock looks shiny and glasslike. Sometimes gas bubbles are trapped in the rock during the cooling process, leaving tiny holes and spaces in the rock.
Examples of this rock type include basalt and obsidian.
Sedimentary rocks are formed from particles of sand, shells, pebbles, and other fragments of material. Together, all these particles are called sediment. Gradually, the sediment accumulates in layers and over a long period of time hardens into rock. Generally, sedimentary rock is fairly soft and may break apart or crumble easily. You can often see sand, pebbles, or stones in the rock, and it is usually the only type that contains fossils.
Examples of this rock type include conglomerate and limestone.
Metamorphic
Metamorphic rocks are formed under the surface of the earth from the metamorphosis (change) that occurs due to intense heat and pressure (squeezing). The rocks that result from these processes often have ribbonlike layers and may have shiny crystals, formed by minerals growing slowly over time, on their surface.
Examples of this rock type include gneiss and marble.
Igneous
Igneous rocks are formed when magma (molten rock deep within the earth) cools and hardens. Sometimes the magma cools inside the earth, and other times it erupts onto the surface from volcanoes (in this case, it is called lava). When lava cools very quickly, no crystals form and the rock looks shiny and glasslike. Sometimes gas bubbles are trapped in the rock during the cooling process, leaving tiny holes and spaces in the rock.
Examples of this rock type include basalt and obsidian.
Use a magnifying lgass to examine the rock.
Describe what you see - colour, shape, size.
A rock is made of mineral materials in a solid state. Geologists use features such as the mineral composition and the shape, size and orientation of the fragments in the rock to classify rocks according to their origin. Both the composition of the minerals and the circumstances under which it was formed determine the features and properties of the rock. Some commonly measured properties include: • Density: the ratio of mass to volume for a material. Measuring identifies tell you if a material is heavy for its size. A rock that floats in water is less dense than water.• Hardness: how resistant solid matter is to various kinds of permanent shape change when a force is applied. A common measure is to see whether the rock scratches different surfaces to determine if it is harder than the material it is being scratched against. Hardness is usually measured for minerals rather than rocks. The hardest mineral known is diamond whilst the softest is talc. The Mohs hardness scale developed by Fredrich Mohs ranks 10 common minerals based on their hardness.
Different rocks have different properties. The features might be due to the composition of the rock (colour, texture, reaction to acid) or due to the shape of the rock (jagged or smooth, large or small). Scientists distinguish rocks based on their intrinsic characteristics (the size and nature of its minerals and their properties) rather than on external characteristics that can be influenced by other things (a rock can be weathered or polished to change its shape).
Different rocks have different properties. The features might be due to the composition of the rock (colour, texture, reaction to acid) or due to the shape of the rock (jagged or smooth, large or small). Scientists distinguish rocks based on their intrinsic characteristics (the size and nature of its minerals and their properties) rather than on external characteristics that can be influenced by other things (a rock can be weathered or polished to change its shape).
Mechanical weathering is the physical breaking down of rocks into smaller pieces. Wind and water can break off pieces of rocks as they move past them. Ice can also cause weathering, for example, if water drips into a crack in a rock it will expand as it freezes, putting pressure on the crack. Also, glaciers can scrape underlying rock as they move through a valley. Abrasion from living things such as animals can break rocks into smaller pieces. Plant roots can grow into crevices in rocks, forcing the cracks wider until the rock breaks.In this lesson, students model a rock being tumbled in a river or stream. As the water flows, it moves the rocks downstream. During this process, the rocks are rubbed together and small pieces are broken off. Eventually, this causes the characteristic smoothness of river rocks. However, the model rock balls used in this activity are much softer and break down much more quickly than real rocks.
Weather investigation planner
Change: the time of shaking•
Measure/Observe: the size of the clay-sand ball after shaking•
Keep the same: the size of the ball, what the ball is made of, the hardness of the ball, how hard it is shaken, the type of liquid, how much water is used, the size of the jar.
Measure/Observe: the size of the clay-sand ball after shaking•
Keep the same: the size of the ball, what the ball is made of, the hardness of the ball, how hard it is shaken, the type of liquid, how much water is used, the size of the jar.
Erosion
Erosion is the removal and transport of rocks and weathered material, for example, soil. It helps to shape landscapes. Erosion is a natural process that can be affected by human activity. Erosion, especially in Australia, is a serious concern given the slow-forming ancient soils prevalent in this country. Farmers are particularly concerned about erosion if it removes the soil required for crop growth. Living things, for example, plants both help and hinder erosion. Plant roots bind soil, reducing wind erosion, but can also help weather rocks. Farmers in windy areas often plant rows of trees between their fields. This slows down the wind at ground level, which reduces the amount of soil lost to erosion.
The structure of the Earth’s surface
There are three main layers at the surface of the Earth: topsoil, subsoil and bedrock. Topsoil contains decomposed remains of living things (mostly plants) mixed with fine particles of broken down rocks. Subsoil contains larger rock particles and usually little or no plant material. The bedrock is the parent material which, when broken down, forms large and small rocks and when further broken down forms the bulk of the soil. These layers can often be seen in road cuttings.
The use of scientific models
The physical world is a complex ecosystem with millions of variables. Scientists use models to help engage with a concept or to produce testable hypotheses. Often the model is a simplified version of reality, and the ability of the model to fit the actual observations tells scientists whether their simplifications were justified or not. Models can be expressed physically, for example, creating the model of a mountain in a tray; by the written word, for example, saying that ‘DNA is like a computer program’; by a mathematical formula; or by a combination of these. These models are all expressions of a current theory to be tested.Models have limitations to their power of explanation and representation. For example, sand does not model soil erosion completely or soil may have plant roots which help stop erosion. A scientist will acknowledge and describe the limitations of any scientific model devised. Information gathered from experiments can support or discredit a scientific model.Using scientific models to represent scientific phenomena can assist students to develop their understanding. Effective teaching includes discussion of the way in which models represent a concept and ways in which they might not.
The structure of the Earth’s surface
There are three main layers at the surface of the Earth: topsoil, subsoil and bedrock. Topsoil contains decomposed remains of living things (mostly plants) mixed with fine particles of broken down rocks. Subsoil contains larger rock particles and usually little or no plant material. The bedrock is the parent material which, when broken down, forms large and small rocks and when further broken down forms the bulk of the soil. These layers can often be seen in road cuttings.
The use of scientific models
The physical world is a complex ecosystem with millions of variables. Scientists use models to help engage with a concept or to produce testable hypotheses. Often the model is a simplified version of reality, and the ability of the model to fit the actual observations tells scientists whether their simplifications were justified or not. Models can be expressed physically, for example, creating the model of a mountain in a tray; by the written word, for example, saying that ‘DNA is like a computer program’; by a mathematical formula; or by a combination of these. These models are all expressions of a current theory to be tested.Models have limitations to their power of explanation and representation. For example, sand does not model soil erosion completely or soil may have plant roots which help stop erosion. A scientist will acknowledge and describe the limitations of any scientific model devised. Information gathered from experiments can support or discredit a scientific model.Using scientific models to represent scientific phenomena can assist students to develop their understanding. Effective teaching includes discussion of the way in which models represent a concept and ways in which they might not.
Exploring water erosion
Ask students if they have seen areas where hills have been cut for a road to go through, or where deep digging has occurred.
Introduce the photos (see ‘Preparation’) and ask questions such as: • Did you see a lot of rock in those cut layers?• How does this information fit with what you think you know?• What questions do you have?Explain that scientists have found that we stand on a relatively thin amount of soil under which is a solid layer of rocks that extends for kilometres. 4Ask students how they think landscapes can change over time, asking questions such as:• What parts of the landscape might change?• How might these changes occur?• Can rocks and soil change? How? • How might we investigate how landscapes change?Discuss the term ‘erosion’ and add a description to the class science journal. Discuss how human activity can impact on erosion and how the impact of erosion caused by water is a serious concern for farmers.
Introduce the photos (see ‘Preparation’) and ask questions such as: • Did you see a lot of rock in those cut layers?• How does this information fit with what you think you know?• What questions do you have?Explain that scientists have found that we stand on a relatively thin amount of soil under which is a solid layer of rocks that extends for kilometres. 4Ask students how they think landscapes can change over time, asking questions such as:• What parts of the landscape might change?• How might these changes occur?• Can rocks and soil change? How? • How might we investigate how landscapes change?Discuss the term ‘erosion’ and add a description to the class science journal. Discuss how human activity can impact on erosion and how the impact of erosion caused by water is a serious concern for farmers.