Tell how snowdrifts and sand dunes are formed in similar ways. Then describe differences in how they are formed.?

Similar: Both are formed by wind.

Different: Sand dunes are formed by deposition. Snowdrifts are formed by weathering.

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They are both formed by deposition of a granular material by the wind.

Weathering is totally different - it is the breakdown of rock (or other materials) by the weather, biological agents, etc. - though sand is a product of the weathering of rock.