Activity 28 Cutting Canyons and Building Deltas

Activity 28 Cutting Canyons and Building Deltas Challenge Question . . . How can moving sediments create problems for construction? Key Vocabulary . . . Sediment Delta River channel Model

Vocabulary: Sediment – materials that settle out of water Delta – the fan shaped area of land at a river’s mouth that bulges into the bay River Channel – the riverbed that is carved into the land Model – helps us to understand a process we cannot investigate directly

READ THE INTRODUCTION ON PAGE 18 Getting Started Could typical rainfall change the shape of the land? Accumulated rainfall can slowly wear away the earth. We will investigate the effect of flowing water on landforms. Sediments can be moved by water, ice (glaciers), wind and gravity. READ THE INTRODUCTION ON PAGE 18

PROCEDURE – Page 19 Glue the “River Models Drawings” sheet into your journal. Predict what will happen with the water and sand after it “rains” at the “X” on the top of the diagram. Draw what you predict will happen on the “Prediction Diagram.” Label sand and water on your diagram. Label any landforms (e.g., river, stream) you think will form.

PROCEDURE (continued) Read steps #3-9 on pages 19 & 20. Focus on the channels being cut by the flowing water and the sand being deposited in the catch basin. Look for the river channel (or, riverbed) that is carved into the land in your model. Label the following landforms on your diagram if possible: river channel, islands, canyons and river banks. IMPORTANT: Be as careful as possible to avoid major spills!

RESULTS: How do your observations relate to the topography of Boomtown? What landforms in Boomtown correspond to the top of the model? What area of Boomtown corresponds to the bottom of the model?

Analysis Questions (Pages 20-21) Work in your groups to answer questions #2 and #3. (Answers should be written in complete sentences in your journal.) You may incorporate your answer for #3B into your answer for #3A. Work in independently to answer question #5. (The answer should be written in complete sentences in your journal.)

Analysis Answers (#2) 2. The water causes the sand to “get carried away” or “slump down.” Stream channels and gullies formed. (You may have seen canyons form, as well.) Any time sand or soil moves from one place, it eventually is left in another location!

Analysis Answers (#3) 3. The flowing water slowly removes the particles of rock through the process of weathering. The flowing water then carries the rock particles away down river via the process of erosion. The walls are so steep and high because rock does not slump or collapse as easily as softer material (e.g., sand). Earth processes that we see happening today, such as cutting a canyon, have been occurring on earth for millions of years! They lead to huge changes of topography, like the Grand Canyon

Analysis Answers (#5) 5a. Delta Marsh – Movement of sediments could wash away the soil of the marsh and make the soil less stable for buildings. Also, movement of the sediments could result in unwanted earth material in people’s yards. 5b. Green Hill – Movement od sediments away from the hillside could cause the hillside to collapse and weaken buildings built above. The sediment could also end up on the houses below. 5c. Seaside Cliff – Movement of sediments from the cliff could weaken or wash away the cliff. (We will discuss this possibility in future activities.)

“Getting Finished” Name the term that is defined as, “solid material such as weathered (i.e., broken down) rocks and soil that is moved and deposited in a new location.” SEDIMENT Name the process that transports sediment from one location to another. EROSION