Topic: What is deflation? How are the dunes formed?

Target group

1st‑grade student of high school and technical high school (basic scope)

Core curriculum

V. Litosphere: relationship between the interior structure of the Earth and the tectonics of lithosphere plates, internal and external processes shaping the Earth's surface and their effects, rocks.

Student:

3) characterizes the main external processes modeling the Earth's surface (erosion, transport, accumulation) and effects of the sculptural activity of rivers, wind, glaciers, glacier and seas, and weathering.

General aim of education

Explaining to pupils the deflation process and the process of dunes formation.

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• explain what deflation means;

• explain how dunes are formed;

• describe the difference between a parabolic dune and a barchan.

Methods/techniques

• activating

  • discussion.

• expository

  • talk.

• programmed

  • with computer;

  • with e‑textbook.

• practical

  • exercices concerned.

Forms of work

• activity in pairs;

• activity in groups;

• collective activity.

Teaching aids

• e‑textbook;

• interactive whiteboard, tablets/computers.

Lesson plan overview

Before classes

• Students get acquainted with the content of the abstract. They prepare to work on the lesson in such a way to be able to summarize the material read in their own words and solve the tasks themselves.

Introduction

• The teacher explains the aim of the lesson and together with students determines the success criteria to be achieved.

• The students, selected by the teacher, refer the lesson they read at home before the classes.

Realization

• The teacher indicates students who briefly discuss the following issues in turn: deflation process and its effects; formation of dunes; barchans and their characteristics; parabolic dunes and their characteristics; starry dunes and their characteristics.

• Students refer to assigned topics. If necessary, the teacher complements their statements.

• The instructor explains to students the idea of working with the snowball method. By working with this method, students assess the impact of vegetation on the deflation process and on the movement of parabolic dunes. Each student ponders for a moment on this problem individually, then students discuss in pairs, agreeing a common position. Couples merge into fours and then into larger and larger groups.

• The students consolidate the acquired information, discussing it with their nearest neighbors („tell your neighbor” method).

Summary

• The teacher asks the students questions:

  • What did you find important and interesting in class?

  • What was easy and what was difficult?

  • How can you use the knowledge and skills you have gained today?

  Willing/selected students summarize the lesson.

• The teacher asks students to carry out the recommended interactive exercise themselves.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

What is deflation? How are the dunes formed?

The blowing away of fine rock material by the wind is called deflation. Where rocks are loose or where the eluvium is composed of very fine particles, where it is dry and there is no vegetation, large‑area deflational depressions may form. When the bottom of the deflational depression in a desert reaches the groundwater level, an oasis may be created.

The sand that is blown away can be carried over long distances. In places where the wind abates and is less able to transport materials, the sand settles down forming hills called dunes. Their long windward slope (the slope exposed to the wind) rises gently. Each grain of sand is rolled upwards until the edge, beyond which, under the influence of gravity, it rolls down the leeward slope (sheltered from the wind) which is short and steep. In extremely dry climates, the wind moves the lower lateral parts of the dunes (where there is less sand) faster than the central parts (the highest). Due to this, the dune assumes a shape similar to that of a crescent Moon, with its arms pointing in the direction in which it is moving. Such dunes are called barchans. In moderate climates with higher rainfalls, the dune’s lateral arms are often overgrown with vegetation, while the central part is movable because it is made up of drier and looser sand and is not immobilized by plants. The dune’s shape also resembles a crescent Moon, but its arms are pointing backwards in relation to the direction of the dune’s motion. Such structures are called parabolic dunes.