Investigation 2: Weathering and Erosion Part 1: Sorting Earth Materials

Focus Question How big are rocks?

Rock Mixture Each group: One cupful of the mixture Two paper plates Two sheets of newspaper Two hand lenses Two metric rulers

Analyze Divide the rock mixture between the two paper plates Each pair examines and records observations in journal Put newspaper under the paper plates for easy clean up

Sorting How did you sort your material?

Wentworth Scale of Rock Particle Size Boulder – Above 256 millimeters (mm) Cobble – mm Pebble – 4-64 mm Gravel – 2-4 mm Very coarse sand – 1-2 mm Coarse sand – mm Medium sand – mm Fine sand – mm Very fine sand – mm Silt – mm Clay –Less than.004 mm

Measuring Time! Each pair needs a ruler with millimeters You have time to measure all four piles Determine which category each falls into based on the scale Add this information to your notebooks

Rock Sizes in Nature Today I handed you a cup of rocks that are all different sizes. Do rocks always appear in nature mixed up by size? Where in nature can you find sand? How does sand get separated from other sizes of earth materials in nature? What would cause sand to become separated from other sizes of materials in a desert? Would wind separate materials in your mixture? Which size of materials would be moved easily by wind?

Sorting The process of separating earth materials by size

Wind Test GENTLY blow on the mixture Which particles move easiest?

Small-Particle Categories Press finger on the dust and rub between fingers If gritty (rough), silt particles If smooth, clay particles

Rock Categories How are each of the particles in the earth- materials mixture alike? How are the particles in the mixture different? How are the sand-sized particles like the gravel pieces?

Wrap-Up Focus Question: How big are rocks? Record vocabulary in Index

Homework Visit your backyard, local park, the school, or somewhere else Inventory the types of rocks you discover