Arabian Peninsula's Northern Desert Plains: Covered in Sand

The correct answer: Sand (Option A).

Arabian Desert Overview

• Covers ~2.3M km² (Western Asia).
• Northern plains: An Nafud, Ad Dahna, and southern fringe of Syrian Desert.
• Surface: predominantly quartz sand (light brown/tan, fine-grained).
• Dunes: barchan, transverse, star dunes up to 100+ m high.

Other Surface Types (Minor)

• Gravel plains (reg/hamada): Exposed bedrock, lag deposits.
• Sabkhas: Coastal salt flats (evaporites).
• Volcanic fields: Harrats (western Arabia) — basalt, not northern plains.
• Wadis: Dry river channels — incised into sand/gravel, not cover.

Sand Dynamics

Prevailing shamal (northwesterly) winds move dunes, create ripples, sort grains. Sand seas (ergs) shift meters/year.

Ecological Note

Sand supports specialized flora (Calligonum, Haloxylon) and fauna (sand cat, sand gazelle, reptiles). Fragile crusts (cyanobacteria, lichens) stabilize surfaces—easily destroyed by off-road driving.