Rocks and Minerals Science Study Guide for 4th Grade
The Rock Cycle via video for Igneous Rock, Sedimentary Rock and Metamorphic Rock
These are the concepts that my kids find confusing, so I’ve added some extra information from sites to help kids understand the differences. This great information is from Mr.SciGuy.
Erosion versus Weathering
This is from Compare Anything.
Weathering and erosion are geological processes that act together to shape the surface of the Earth.
Erosion is displacement of solids (soil, mud, rock and other particles) usually by the agents of currents such as, wind, water, or ice by downward or down-slope movement in response to gravity or by living organisms.
This video shows weathering verus erosion through some great demonstrations. It’s 9 minutes long.
This is a confusing concept, so here’s more:
What’s the difference between weathering and erosion?
Weathering involves two processes that often work in concert to decompose rocks. Both processes occur in place. No movement is involved in weathering. Chemical weathering involves a chemical change in at least some of the minerals within a rock. Mechanical weathering involves physically breaking rocks into fragments without changing the chemical make-up of the minerals within it. It’s important to keep in mind that weathering is a surface or near-surface process. As you know, metamorphism also produces chemical changes in rocks, but metamorphic chemical changes occur at depth where either the temperature and/or pressure are significantly higher than conditions found on the Earth’s surface.
As soon as a rock particle (loosened by one of the two weathering processes) moves, we call it erosion or mass wasting. Mass wasting is simply movement down slope due to gravity. Rock falls, slumps, and debris flows are all examples of mass wasting. We call it erosion if the rock particle is moved by some flowing agent such as air, water or ice.
So, here it is: if a particle is loosened, chemically or mechanically, but stays put, call it weathering. Once the particle starts moving, call it erosion.
This is from The National Park Service.
Here’s a fun video from Scholastic:
Rock versus Minerals
The Museum of Science does a great school classroom presentation called Rock Detectives. One great example they gave of rocks versus minerals is this:
Chocolate Chip Cookie
What ingredients are used to make a chocolate chip cookie? Kids will answer with things like: flour, butter, sugar and chocolate chips.
The chocolate chip cookie is LIKE A ROCK made up of ingredients. Ingredients are LIKE MINERALS.
What happens if instead of baking, you fry it instead? You get … chocolate chip pancakes. So, depending on what happens to the mix of minerals (for example, different pressures and/or heat), there are different outcomes. JUST LIKE minerals and rocks.
A rock is a mixture of one or more minerals. They are classified by the way that they are made.
A mineral is
- Naturally occurring
- Definite chemical composition & crystalline structure
Mineral Identification Tests
The Color Test- easiest test to do but not always reliable
The Streak Test
- The color of the powdered mineral.
- Performed by rubbing the unknown mineral on an unglazed tile.
The Luster Test
- the way a mineral shines or doesn’t shine
- the only way to really learn the different lusters is to see them for yourself.
Types of Luster
- Metallic- looks like shiney metal
- Non-metallic- all the other ways that a mineral can shine
- Glassy/vitreous- shines like a piece of broken glass (most common non-metallic)
- Dull/earthy- no shine at all
- Resinous/waxy- looks like a piece of plastic or dried glue
- Pearly- looks oily it may have a slight rainbow like an oil slick on water. Also looks like the inside of some clam shells
- Adamantine- brilliant, sparkling shine like a diamond
Hardness- a minerals resistance to scratching. This should not be confused with brittleness. A diamond is very hard and will scratch a hammer but a hammer will smash a diamond. Likewise, talc, one of the softest minerals, is not squishy. It will still put a serious hurting on you if you get hit in the head with it.
Types of Rocks
“Fire Formed”- melted rock material cools and solidifies (“freezing”)
- Intrusive- rock formed inside the Earth
- Extrusive- rock formed on the surface
- Texture- the size of the crystals- NOT HOW IT FEELS
Made from sediments or rock material that has been broken down in some way.
- Sedimentary rocks are usually formed in a watery environment.
- Often layered
- Are the only rocks that normally contain fossils
- changed from a pre-existing rock
- caused by extreme heat and/or pressure
Cleavage versus Fracture
Cleavage -To break along flat surfaces.
Examples of Cleavage (these examples are not on the test but I think they are helpful to illustrate cleavage visually).
- Cubic- To break into cubes
Rhombihedral- to break into “pushed over cubes”
Basal- to split into thin sheets
Fracture -The way a mineral without cleavage breaks.
Examples of Fracture (This is not on the test, but it might help your child get a visual sense of a fracture — think bowl shape, needs, or sharp edges).
- conchoidal- to break in a scooped out bowl shape- like a conch (sea snail)
- hackly fracture- to have irregular sharp edges
- splintery- to break into long, thin needles
This is not on the test, but here are more details on rocks versus minerals to help your child solidify this concept. This is from Rocks For Kids.
All rocks are made of 2 or more minerals, but minerals are not made of rocks.
Rock Words: There are many common names for rocks and the usually give you an idea of how big the rock is. Here are a few:
- mountain – huge, giant hunk of rock that is still attached to the earth’s crust, doesn’t move, tall
- boulder – large, taller than a person
- rock – large, you could get your arms around it or a bit smaller but it is usually jagged,
broken off a bigger piece of rock
- river rock – round rocks that are along the edge & at the bottom of fast-flowing rivers
- stone – medium, you could hold it in two hands
- pebble – small, you can hold it with two fingers, could get stuck in your shoe, usually rounded
- sand – made up of tiny pieces of rock, grains of sand
- grain – tiny, like a grain of rice or smaller, often found on a beach
- dust – really fine powder that is mixed in with sand or soil
- speck – as in a speck of dirt
- A mineral is the same all the way through. That is one reason we speak of
a sample or a specimen rather than a rock.
- There are about 3000 known minerals on earth.
- All rocks are made up of 2 or more of these minerals.
Finally, here is a video of rocks versus minerals by kids.