Our area of study is:
Rocks and Minerals and Soil (Oh My!)
Mr. Andersen's HR: Complete the first side of the Research Questions. Study for Chapter 9 Test next week. See list of questions that were posted in class.
Mr. Chin's HR: Read and Answer - How soil is Made and Lesson Summary ajnd Checkpoint. Study for Chapter 9 Test next week.
A. Minerals need to have four criteria in order to be considered a mineral. All minerals must be:
1. naturally formed or occurring,
2. inorganic - made from nonliving material,
3. solid in structure and state of matter
4. having a definite crystalline structure and chemical composition
B. Three main types of rocks and how they are formed:
1. igneous rocks- formed from cooling magma; igneous literally translates to "formed from fire"; when magma or lava cools, igneous rocks are formed;
there are two types of igneous rock:
a. intrusive - because they are formed inside of the earth it takes longer for the magma to cool; this slower cooling time is the reason that intrusive igneous rocks have a finer grain texture and larger crystals,
b. extrusive - these igneous rocks are formed outside of the Earth and have a shorter cooling time (they cool quicker); this shorter cooling period tends to form igneous rocks that have a coarse or rough texture and smaller crystals
2. sedimentary rocks- formed from dust and tiny bits of rock (sediment) that settle in water. The oldest part are the parts that are found deepest. Sedimentary rocks are formed in layers; sedimentary literally translates to "sitting rock"; fossils are found only in sedimentary rocks, sediment comes from weathering and erosion of other rocks
3. metamorphic rocks- deep within the mantle, sedimentary and igneous rocks are put under great heat and pressure which changes them to metamorphic rocks; metamorphic literally translates to "changed form"; the heat of the Earth at this level is not hot enough to melt the rocks or turn them back into magma; it is just hot enough to "cook" the rock and change it into a metamorphic rock
C. The Rock Cycle
The Rock Cycle is an ever-changing course of steps that all rocks take as they change to one of the three different types of rocks. All rocks are considered to be (or are considered to be on their way to becoming) a sedimentary, igneous or metamorphic rock.
Example: Metamorphic rocks are rocks that have been heated and pressurized. These rocks may be weathered and eroded into fine particles which find their way to a stream bed. These particles eventually are pressed and become part of a sedimentary rock. Over time, an upheaval may carry this sedimentary rock to a a subducting zone where it descends into the mantle. The heat from the mantle and core of Earth melt this rock. The parts eventually find their way back into the mantle where it cools and becomes an igneous rock.
Soil is formed when weathered rock gathers and mixes with organic material.
Weathering is the process in which rock breaks down to form soil. Frost, drought, water, or temperature changes can cause weathering.
As the rock has become weathered, the pieces become smaller and smaller. spaces between the particles are often filled with air and water.
E. Soil has three main layers
Horizon A -The top layer is known as topsoil. This layer has the most humus and is usually the darkest because of the high amount of organic material. This is also where water begins to break down the organic material and through leaching, carry it to the lower levels.
Horizon B - The second layer is known as subsoil. This layer has less organic material than topsoil, but it does have some. It's usually lighter in color because it has less organic material.
Horizon C - The third layer is called the parent rock material. This layer has little organic matter. Being the lowest of the three main layers, the effects of leaching are decreased here.
F. There are three main kinds of soil
clay - fine grain and hold water well
silt - larger grains and only holds some water.
sand - made of the largest grains and hold water poorly.
loam - a combination of silt, sand and a little bit of clay
Prepare for your Chapter 9 TestStart your studying with the following questions. This will help to focus upon the most important aspects of the chapter.
1. What are the four criteria for minerals?
2. What are the three main types of rocks? How are they made? What are their characteristics?
3. How do rocks change from one form to another? What causes the changes to happen? Think Rock Cycle
4. What are the names of the top three layers of soil? What are their characteristics?
5. How do scientists use Mohs Harness Scale? What does it tell them?
6. Why are lichen considered to be pioneer organisms?
7. What are the four main steps taken to form soil?
8. How do scientists know which rocks are older?
9. What does leaching do for soil?
10. What is loam, humus, organic material?
Be sure to check your research questions and lesson summaries from Chapter 9.