Our Earth Grade 4 Mrs. Hansen

Chapter 8 – Minerals & Rocks Minerals – are natural, nonliving solid crystals that make up rocks Earth’s crust is made of rocks Rocks are made of minerals

Can you name the different layers? Which layer do we walk on? Minerals Have crystals Each mineral has the same chemical makeup 3,000 types of minerals “rock forming” minerals are the only minerals that make up rocks Rocks 3 Types of Sedimentary Rocks Mudstone, sandstone and limestone Igneous rocks – form from molten rock Metamorphic rocks – have changed because of heat and pressure Our Earth Layers of our earth Can you name the different layers? Which layer do we walk on?

Name some Minerals Granite – one of the most common rocks Quartz is hard and glassy Mica – form rocks that are usually brown or black Feldspar is often white or pink

How do we know it is a Mineral? To identify a mineral scientists look at “Physical Properties” how it looks Color – certain minerals show a certain color Luster – how the mineral reflects light (is it dull, metallic, pearly, glassy or silky) Streak – scratch the mineral on a surface – what color of powder does it leave behind Mohs Scale – How hard is the mineral on a scale from 1 – 10 (how easy can it (the mineral be scratched) turn to page 241 in your book.

Rocks Sediment – eroded material (rocks, fossils, dead plants, shells and animal matter wash down to rivers, lakes and oceans through erosion. This material that settles to the bottom is called sediment. Sedimentary rocks are sediment that has stuck together and harden.

Can Rocks turn into soil? Yes! Over time weathering can cause rocks to loosen and break apart. Weathering is the breaking up of rock, caused by exposure to natural forces present at the Earth’s surface, such as water through freezing and heating, water run off and plant roots breaking through a weakened rock.

How do we control weathering? Building jetties to strengthen land that is near the water Building dams to hold back water Plowing fields in the opposite direction the wind blows. Creating terraces with rocks or other materials to slow down the flow of water Planting grasses, trees and other plants to prevent soil from washing away.

What do you think? As our class walks to the cafeteria we notice that the sidewalk has small holes and is bumpy. What do you think has caused this? Wind Chemicals Deposition weathering

Weathering Weathering is when forces of nature break down rocks through water, ice, temperature changes chemicals or living things such as plants that cause weathering. Wind erosion is when the wind blows the soil Chemical weathering is when chemicals cause rocks to change into different materials. For example rain water mixes with Carbon dioxide (CO2) in the air to form a weak acid. This is called “acid rain”

Is weathering the only thing that will change rocks? No Erosion is when water, ice, gravity, and wind often work together to move weathered pieces of rock.

How fossil forms Turn to page 244 look at the pictures of the dinosaur and how it can become part of sedimentary rock Fossils help scientists form hypothesis. How?

Fossils tell a story Looking at the fossils in the rock layers tell scientists how old the layers of rock are. Examples – ammonoids, sea creatures that looked like snails are estimated to have lived only from about 408 to 66 million years ago. An ammonoid fossil found in a layer of rock means the layer formed between 408 and 66 million years ago.

Geologic (means rock) Scientists have divided their estimates of Earth’s history into periods of time. The periods are put into a geologic (rock) time scale. Earliest (means oldest) period is at the bottom. Turn to page 245 and look at the scale and captions at the right of the page.

Igneous and Metamorphic Rocks Igneous rocks – form from molten rock, the word igneous means fire A layer of rock below earth’s crust is so hot that it is partially melted. Igneous rocks may form above or below earth’s surface.

2 ways Igneous Rocks form Volcanoes where the molten rock can ooze out like a red hot river and explode out in hot globs Magma slowly rising toward the earth’s surface (this is the most common). The magma rises and fills in cracks and melts the surrounding rock or forces it aside to make space, it cools. It can take more than a MILLION years for this to happen. Turn to page 248 on the left side

Metamorphic Rocks Natural forces cause rocks to change form COMPLETELY. These rocks change because of heat and pressure. Metamorphic rocks can be sedimentary, igneous and other metamorphic rocks. Example Limestone (a sedimentary rock) can turn into marble through heat and pressure. Turn to page 249 and copy this page in your journal.

CHANGES TO EARTH Vocabulary Landform different sizes and shapes of the earth’s surface. (canyons, valleys, plateaus, coasts, peninsulas, low ground {plains}, high ground {hilly or mountainous}) Weathering rocks in earth’s crust are slowly being broken into smaller pieces by nature (water, ice, temperature changes, chemicals and living things such as plant

2 types of weathering Is the SLOW way earth changes Physical weathering – only the size of the rocks are changed. Chemical weathering – rocks are broken into smaller pieces and the material that makes up the rock or soil is also changed. (Changes rocks into different materials.)

How Do Weathered Materials Move? Erosion – movement of water, ice, gravity and wind work together to move weathered pieces of rock. Deposition – (to deposit) while some of earths surface erodes the eroded material is deposited somewhere else.

Erosion can bring Landslides – soil and rock that move down hill by the force of gravity Avalanches snow and ice that break away and move down hill by the force of gravity

How Do We Protect Our Land? Terraces slow down the speed of water. Turn to page 269 Jetty Plowing fields the opposite way the wind blows Planting grass and trees on soil that easily blows

Rapid (Quick Changes) in our earth Earthquakes Fault: a break or crack in rocks where Earth’s crust can move (the earth’s plates) Epicenter: the focus or center of the earthquake where it is the strongest. Volcanos Magma Lava eruption