Presentation on theme: "A Unit study on Rocks and Minerals for 3 rd grade."— Presentation transcript:
A Unit study on Rocks and Minerals for 3 rd grade
Essential Question: What are the similarities and differences between rocks and minerals?
Enduring Understandings Rocks are made of minerals. Rocks & minerals can be classified using physical attributes such as color, shape, texture, & hardness. The environment can change rocks over time. You can perform a streak test to compare hardness of rocks and minerals.
Table of Contents 1.Rocks 2.Types of Rocks 3.Rock Cycle 4.Minerals 5.Differences 6.Weathering and Erosion
What are rocks? Rocks and stones are naturally occurring solids made up of minerals. The Earth's crust is made up of rock. Rocks have been used by humans for millions of years, from early tools and weapons through to various construction materials. There are three different types of rocks based on the way they form, igneous, sedimentary and metamorphic.
Since a rock can be composed of several minerals, it is classified according to the process of its formation.
Igneous Rocks Igneous rocks are also formed when volcanoes erupt, causing the magma to rise above the earth's surface. When magma appears above the earth, it is called lava. Igneous rocks are formed as the lava cools above ground. Underground, they are formed when the melted rock, called magma, deep within the earth becomes trapped in small pockets. As these pockets of magma cool slowly underground, the magma becomes igneous rocks.
Sedimentary Rocks For thousands, even millions of years, little pieces of our earth have been eroded--broken down and worn away by wind and water. These little bits of our earth are washed downstream where they settle to the bottom of the rivers, lakes, and oceans. Layer after layer of eroded earth is deposited on top of each. These layers are pressed down more and more through time, until the bottom layers slowly turn into rock.
Metamorphic Rocks Metamorphic rocks are rocks that have "morphed" into another kind of rock. These rocks were once igneous or sedimentary rocks. How do sedimentary and igneous rocks change? The rocks are under tons and tons of pressure, which fosters heat build up, and this causes them to change.
The Rock Cycle is a group of changes. Igneous rock can change into sedimentary rock or into metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock. Metamorphic rock can change into igneous or sedimentary rock. Rock Cycle
The changes that rocks go through is called the rock cycle, and it goes something like this:
Erosion refers to the process of water breaking down rock over time. The weather, including sunlight, also causes rocks to break down. Compaction, on the other hand, is when accumulated sediment is pressed together to form sedimentary rock. Usually, this happens when sediment flows into a river or other body of water. The pressure of the water "squeezes" the sediment together, compacting it. The earth pushes rocks up to the surface, where they go through changes caused by erosion, the weather, and compacting.
Eventually, these forces press the rocks back down into the earth, where they are heated by pressure within the earth. The intense pressure and heat underground presses the rocks together and, over time, can melt them into magma. Some of that magma may reach the surface, where it cools off and becomes solid, igneous rock again!
What are minerals? Minerals are naturally occurring substances formed by geological processes. Physical properties of minerals include hardness (Mohs scale), luster (how it reflects light) and color, as well as more complicated properties such as streak, fracture, cleavage and density. Mohs scale of hardness measures the ability of minerals to scratch each other. Talc is very soft and is listed as 1, diamond is very hard and is measured as 10. There are over 4,000 different types of minerals. Only around 30 of these are commonly found in the Earth's crust.
Minerals have certain properties, or attributes, that help to identify them. Minerals can be identified by their color, luster, streak, hardness, and clevage.
Color Color is not always a good clue to the identity of a mineral. Many minerals are found in several colors and many have extra chemicals in them that give them an unexpected color. Also, weathering may change the color of the mineral. Example- quartz comes in various colors: rose, milky, and clear.
Luster Luster is the way a mineral reflects light. Minerals can be described as metallic, pearly, glassy, silky, greasy, brilliant, or dull. Chrysocolla-dull Diamond-brilliant Talc-pearlyPyrite-metallic Quartz-glassy Opal-greasyGypsum-silky
Streak Streak is the color made by rubbing a mineral across a hard, rough surface like a bathroom tile. Example- pyrite is a brassy, yellowish color. However, it makes a greenish, black streak when rubbed across a streak plate.
Hardness Hardness is measured by seeing how easy it is to scratch a mineral. Each mineral is used to scratch the other minerals to see the order from softest (talc) to hardest (diamond). A German mineralogist, Friedrich Mohs, developed a standard scale of hardness in 1822.
Cleavage Cleavage is when certain minerals break in a definite way. Feldspar breaks into little steps. Calcite cleaves into slanting bricks. Halite breaks into cubes. Muscovite breaks into blocks.
What are the differences between rocks and minerals? It is not easy to tell the difference between rocks & minerals because there are so many kinds of them. A mineral is one solid formation that occurs naturally in the earth, while a rock is a solid combination of more than one mineral formations which is also occurring naturally. A mineral is defined by its structure and shape. Since a rock can be composed of several minerals, it is classified according to the process of its formation.
What is weathering and erosion? Weathering is the process where rock is dissolved, worn away or broken down into smaller and smaller pieces. Once the rock has been weakened and broken up by weathering it is ready for erosion. Erosion happens when rocks and sediments are picked up and moved to another place by ice, water, wind or gravity. When ice melts or wind and water slow down they can't carry as much sediment. The sediment is dropped, or deposited, in landforms.