Ch. 9Lesson 1

How does Earth’s surface wear

away?

• natural features on Earth’s natural features on Earth’s surfacesurface

• mountains, plains, mountains, plains, plateaus, peninsulasplateaus, peninsulas

landformslandforms

Along coasts, landforms such as peninsulas extend into the water.

weathering

•process that breaks down rocks in Earth's crust

examples of weathering

2 types of2 types ofweatheringweathering

mechanical(physical)

chemical

physical weathering- •no change in chemical

composition--just broken into smaller pieces

causes of physical

weathering:

1. water

2. ice

3. temp. changes

4. plant roots

Physical Weathering 02:39

chemical weathering• rock broken into smaller

pieces

• material that makes up rock or soil changes

causes of chemical

weathering:

1. acids in rainwater

This photograph shows a small section of masonry from a church in northern

France. The rock was originally a smooth pillar like structure forming part of the

outside decoration of the building. Over the last

hundred years or so, acidic rain water has constantly

dripped onto the rock from a rain gutter several meters

above it.

• Carbon dioxide (CO2) dissolves in rain water & creates carbonic acid acid rain

• Carbonic acid easily weathers limestone & marble

2.chemicals from plants

• lichens grow on rocks -make weak acids that chemically weather rock

Rock meets lichen YouTube video

• oxidation= iron combines w/ oxygen & H20

• makes rust

Oxidation turned these rocks in Nevada's Valley of Fire red.

Chemical Weathering [02:57]

Weathering Walk• Find 3 places where weathering has occurred

location appearance physical or chemical

sidewalk

AC Rusty chemical

Tree-sidewalk

Tree roots-cracking sidewalk

Physical

Bench Rust chemical

Trench in pit

Incline Physical