Unit 2 Weathering Erosion Vocabulary Weathering Mechanical physical

Unit 2: Weathering & Erosion

Vocabulary ✦ Weathering ✦ Mechanical (physical) weathering ❖ oxidation ✦ Chemical weathering ❖ p. H scale ✦ agents of erosion ❖ Acid ✦ erosion ❖ Base ✦ deposition ✦ ice wedging ✦ surface area ❖ permeable ❖ climate

Weathering and Its Effects ✦ Weathering is the surface processes that work to break down rock ✦ Rocks are broken down into smaller particles called sediments. ✦ Sand- grains larger than silt ✦ Silt- grains larger than clay ✦ Clay- smallest sediment grains ✦ Over millions of years, weathering has changed Earth’s surface ✦ Mountains become hills

Mechanical (physical) and Chemical Weathering Mechanical weathering (left) occurs when rocks are broken apart by physical processes. Chemical weathering (right) occurs when chemical processes dissolve or alter (change) the minerals in a rock or change them into different minerals.

Mechanical (physical) weathering ✦ After a rock has been physically weathered ✦ overall chemical makeup remains the same ✦ Each sediment has similar characteristics to the original rock ✦ Ex. Growing plants ✦ Burrowing animals ✦ Ice expanding

Plants and Animals

Ice (frost) Wedging ✦ Ice wedging occurs in temperate and cold climates where water enters cracks in rocks and freezes ✦ Freezing expands, causing the rock to crack

Chemical Weathering ✦ After a rock has been chemically weathered: ✦ chemical composition of the rock is different ✦ rock can be weakened ✦ Ex of agents of erosion: ✦ acid rain ✦ living organisms ✦ carbon dioxide ✦ water ✦ oxygen

Chemical Weathering Agents Living organisms Oxygen + Iron

Oxidation ✦ Oxidation- when iron combines with oxygen in the presence of water ✦ Ex. iron chains turn into rust ✦ creates a new material and usually gives rocks or objects a reddish-orange color

Erosion ❖ Once rock is weathered and broken down, the smaller pieces are carried away by wind, water, ice, or gravity (agents of erosion) ❖ Erosion- process of bits of broken rock being carried away ❖ Deposition- when agents of erosion deposit or lay down sediment ■ changes land

Surface Area ✦ Surface area- area of a rock or other object that is exposed to the surroundings ✦ As mechanical/physical weathering occurs, rocks are broken down into smaller and smaller particles ✦ smaller pieces have more surface area, exposing more of the rock to water and oxygen ✦ increase in surface area speeds up chemical weathering

p. H Scale ✦ p. H scale-used to measure the strength of acids and bases ✦ (1 -14) ✦ low p. H = acidic ✦ high p. H = basic ✦ Acids: chemical liquids with a lot of hydrogen ions ✦ Bases: chemical liquids with a lot of hydroxide ions ✦ Most minerals dissolve easier in more acidic soil ✦ Different plants also grow best in certain p. H values

p. H Scale

Effects of Climate ✦ Climate- pattern of weather that occurs in a particular area over many years ✦ cold climates- mechanical weathering breaks down rocks very quickly through ice wedging. ✦ warm, moist climates- chemical weathering is more common

Effects of Rock Type

Rock ❖ Permeable- material is full of tiny, connected air spaces that allow water into it

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