3rd Grade Science
Rocks, Fossils, Soils of Georgia
Unit 1
What's in a Rock?
You've probably seen rocks everywhere: in your yard, on the school playground, scattered around the outdoors. But, have you really taken a good look at one? Swipe through the slides to the left to view a wide variety of rocks in different environments! Ask yourself...
What do you see? What impact do the images in the pictures have on the environment?
How do you describe rocks?
Rocks can be described by three characteristics: luster, texture, and hardness
Luster: How reflective of light (shiny) a rock is.
Texture: How a rock feels to the touch (smooth, rought, soft, etc.)
Hardness: How difficult a rock is to break. Rated by the Moh's Hardness Scale (to the right). The higher the rating, the stronger the rock.
Using these, terms, how would you describe the rocks in PowerPoint (above) and picture (right)?
Play this game to learn more about the classification of rocks!
The History of Planet Earth
Just like a human, the Earth has gone through many changes throughout its "lifetime". When you were born, you looked very different than you do now. What's more, you can now play, eat, walk, run, and talk in a way that babies can't.
In the same way, the Earth did not always look or function the way it does now! The Earth we know today is the result of tectonic plates shifting, animal behavior and extinction, weathering and erosion.
What are Tectonic Plates?
Tectonic plates are the large chunks of rock that make up the Earth's crust (the outer layer of the Earth on which we live!). When they collide, mountains are formed, earthquakes occur, and volcanoes erupt. When they move away from each other, oceans and trenches develop.
Water Interacts With the World
Try this Weathering and Erosion Game!
What Happens Once Tectonic Plates Shift and a Land Mass is Formed?
Great question! The appearance of land is largely dependent on WATER! When water and air meet the land, two things can happen ... weathering and erosion.
WEATHERING: When land is broken down into smaller pieces (sometimes, wind and water can create soil by grinding land).
EROSION: When land particals are transported from one place to another. (Both wind and water can move land fragments)
SEDIMENT: Pieces of broken down rock, rock particals.
The downhill movement of water as it flows to the ocean shapes the appearance of land.
How Organisms Impact the Environment
Wind, water, and other natural elements aren't the only factors that shape our world. Organisms (living things) do too! Take a look at the situations below and make a conjecture (educated guess) about how these organisms affect their ecosystem!
A beaver builds a dam and changes the flow of water.
Alterations in water direction can change landscape, topography (the makeup of land), and interfere with or promote erosion/weathering.
A tree is planted in a field and its roots begin growing.
When the roots of plants permeate the soil, they too can break down rock and contribute to weathering.
A new highway is built through a forest.
Human activity can reduce biodiversity (number of different organisms) and shrink habitats.
Dig for fossils in the game below!
Fossils: the preserved remains and impressions of any previously living organism from a previous time (usually extinct (no longer living)).
As fossils, animal remains can become a part of the rock. These remains (which include bones, shells, and rock imprints) can be compared to one another to help scientists learn about what kinds of animals were alive long ago!
Fossils are found at various levels below the Earth's surface. This is because the rock that makes up the Earth's Crust exists in layers due to differing times of formation (some rocks are newer than others). Rocks at the bottom of the Crust are the oldest, while rocks closer to the Earth's surface are younger.
FLASHBACK: There are three types of rock that form in the "Rock Cycle": igneous (volcanic rock), sedimentary rock, and metamorphic rock. Fossils are ONLY found in Sedimentary rock.
Evidence of Common Ancestry
Have you ever been told that you look like your mother, father, or sibling? This is because you are RELATED and your traits can be traced back to your parents, grandparents, great grandparents, and so on.
In the same way, by comparing fossils, scientists can find simmilarities and differences between prehistoric (before history) organisms and animals that live today. These comparisons show that modern organisms are related to ancient organisms (common ancestry) and that some organisms are more closely related than others.
What similarities do you see between these fossils?
The fossils are similarly shaped and have similar smoothness. The ancient whales in Italy and Japan probably have a common ancestor with the living whale.
Even if organisms do not share a direct ancestor, animals and plants are still heavily impacted by each other. These impacts and changes to an organism's environment can be beneficial (helpful) or harmful.
Are the scenarios below helpful or harmful?
Humans cut down all the trees in the rainforest so the Tucan no longer has a home.
Harmful
Birds drop seeds wherever they fly so new plants grow throughout the ecosystem.
Beneficial
Human factories burning fossil fuels pump smoke into the air, causing acid rain.
Harmful
During the Springtime, Bees pollinate flowers, allowing them to grow.
Beneficial
As environments change and habitats are created and destroyed, organisms can also change! This is called Adaptation.
Habitat: the environment in which an organism is naturally comfortable living
Some organisms are better suited to certain environments than others. For example, a polar bear is better acclimated to the Arctic snow than to the Amazon Rainforest. Similarly, a fish would be unable to live in the desert.