| 1. | The wing will continue to grow under both wind conditions, thus producing a seif dune.
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| 2. | Seif dunes are thought to develop from barchans if a change of the usual wind direction occurs.
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| 3. | Seif dunes may thus form long rows whose parallel ridge lines follow the wind's direction.
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| 4. | In the sheltered troughs between highly developed seif dunes barchans may be formed because the wind is unidirectional.
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| 5. | The exposures of Permian sands exhibit complex cross-bedding that is believed to represent ancient seif dune deposits.
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| 6. | When there are two directions from which winds regularly blow, a series of long, linear dunes known as seif dunes may form.
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| 7. | On a seif dune the slipface develops on the side facing away from the strong wind, while the slipface of a barchan faces the direction of movement.
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