WEATHERING AND EROSION EPIC WEATHERING AND EROSION REVIEW FOR 6TH GRADE LET'S GOOOOO

What even is a rock? Elements + chemical compounds → hard, solid materials of Earth's surface Minerals Elements and compounds found in rocks All minerals are solid

Weathering chemical or mechanical breaking down of rocks by exposure to air, moisture, organic materials small-scale, local changes on rocks

Mechanical/Physical Weathering breaks rocks into smaller pieces without changing them chemically frost wedging, plants, animals, gravity

Frost Wedging Water seeps into cracks in rock and freezes When water freezes, it expands and breaks the rock

Living Organisms Growing roots put pressure on rock Burrowing loosens and weakens rock

Gravity Exposes new surfaces for physical and chemical weathering Avalanches, rock slides

Chemical Weathering decomposition of rock due to chemical reactions between rock and chemicals in the environment changes chemical composition of rock materials acted upon

Chemical Weathering, cont'd natural acids and oxygen water + carbon dioxide = carbonic acid acid rain – caused by pollution sulfur released into air by factories, combines with water

Erosion rock and soil materials are loosened and transported from one place to another KEY = MOVEMENT large-scale changes over great distances From canyons and valleys all the way to deltas and sand dunes

Wind sand grains carried by strong winds act like sandpaper scrape away little pieces of rock and soil from hills and mountains can pick up soil from plants or fields and transport to other areas

Water Runoff: water that flows over Earth's surface Carries sediment, soil → eroding land

Water, cont’d Three factors influence amount of water erosion: Rainfall intensity and runoff – more rain, more erosion Steepness of slope – steeper slope, more erosion Vegetation/obstacles – more rocks and plants, less erosion

Soil mixture of weathered rock, organic matter, and water sand, gravel, humus end result of weathering and erosion humus - organic component of soil comes from decomposing plant and animal material

Structure of Earth Crust: surface of Earth Mantle: semi-solid middle layer Convection currents in mantle cause movement of tectonic plates Core: middle of Earth, iron and nickel Extreme heat and under extreme pressure

Convection Currents Convection currents: hot material rises and cool material sinks CC in the mantle force materials up onto the Earth’s crust Creates new crust, pushing tectonic plates into one another This causes continental drift!

Rock Types Igneous rock: formed by the cooling of lava or magma Sedimentary rock: rock formed when sand, mud, and pebbles are deposited on top of each other Layers squashed into each other until they form rock Metamorphic rock: changed by extreme heat and pressure

Steps 1-3 of the Rock Cycle Molten rock from the mantle rises to the surface and creates new crust - This molten rock cools and forms igneous rock As a result of weathering, rock breaks down Over time, broken down rocks are layered on top of each other to form sedimentary rock

Steps 4-7 of the Rock Cycle As more and more rock builds up, pressure and temperature increase a lot This increased pressure and temperature form metamorphic rock Metamorphic rock sinks into the mantle and melts into magma, becoming part of the mantle Through convection, the magma is pushed back up to the surface and creates new igneous rock AND THE CYCLE REPEATS

Rock Cycle Diagram