العلوم (بالإنجليزية) الصف الرابع الابتدائي، الأسبوع 29: Project: shaping a canyon

Rocks, eruptions and canyon projects

الأسبوع 29 · المحور الرابع، الوحدة الرابعة، المفهوم 4.3 «البراكين» (ب) ومشروع الوحدة «القوى التي تشكل سطح الأرض» · 3 دروس

Project: shaping a canyon

Discovery Education Science P4: Term 2, Unit 4, pp. 179–195

GoalUse what we know about weathering, erosion, deposition and volcanoes to explain a pretend canyon, then design a model of how it will change.

New words

factor · something that helps to cause a changelandform · a natural shape of the landmodel · a smaller or simpler copy that shows how something works

Explanation

Real canyons often tell several stories at once. Wadi Nakhr in Oman is a deep canyon with steep walls and layered rock. Scientists also found signs that a volcano was active there millions of years ago. To explain a landform, ask which factors helped to shape it: water, wind, ice, weathering, erosion, deposition or volcanoes. For each feature, give your prediction and your reasoning. Then use a model to think about the future. A model can be a tray of sand that you tilt, a stream of water and a stone as an obstacle. Choose a factor, predict what it will do to the canyon, and test. Teams do better when everyone has a job: a captain, a materials manager, a builder and a reporter. At the end, review what worked well and what to improve.

Factor	What it does to a canyon
running water	erodes the floor and sides, makes it deeper
wind and weathering	wear the walls and break off pieces
deposition	lays down layers and piles at the bottom
volcanic activity	leaves hard igneous rock such as basalt

Worked examples

Clue	Factor	Reasoning
A: dark basalt chunks	volcanic activity	basalt forms when lava cools
B: smooth steep walls	running water and wind	they wear rock smooth
C: coloured bands	deposition	layers laid down at different times
D: heap at the foot	weathering and gravity	pieces broke off and fell

Reading the pretend canyon. The team finds four clues. (A) Dark chunks of basalt lie near the rim. (B) The walls are steep and smooth. (C) The walls have coloured bands. (D) A heap of rocks lies at the foot of a cliff.

now→river cuts deeper→wind wears the walls→canyon in the future

Predicting the future. The team predicts the river will keep making the canyon deeper, and the wind will keep wearing the walls. In 1 000 years the river deepens it by about 2 m. A tree could grow in a crack and widen it.

Job	Who
captain	Karim
materials manager	Habiba
builder	Youssef
reporter	Jana

Team jobs. Karim is captain and keeps the time. Habiba is materials manager and brings the tray, sand and cups. Youssef builds the model. Jana writes the report. At the end they say: what went well? what to improve?

Class activity

Canyon model (outdoors or on a big tray, a grown-up near). Fill a tray with damp sand and tilt it on a book. Press in a stone as a hard rock layer. Pour water down from the top for one minute: this is the river. Then, wearing goggles, blow gently with a straw across the sand: this is the wind. Draw the canyon before and after. Write one sentence on each factor you modelled and predict how your canyon will look after 1 000 years. Share your findings with the class.

Practice

Which factor explains coloured bands in a canyon wall?

Dark chunks of basalt lie near the rim. What do they suggest?

A river deepens a canyon by 2 mm a year. How much in 500 years?

Name two jobs in a team and what each does.