Volcanic deposits
Radar-bright deposits with diffuse margins
Deposits with blurred edges. They are probably volcanic debris that spread out as pyroclastic flows.
These deposits (marked a–d) have no lobes and no channels. Their appearance points to a thick, rough layer of sediment. It probably covers the surface a few metres deep and is made of fragments a few centimetres in size.
They may have formed when the eruption column of a nearby volcano collapsed. The volcano shattered and ejected coarse, gas-rich material. This material fell back, became fluidized in the hot atmosphere and travelled far.
Elsewhere, however, similar material is read as a sand sea. So how the material is interpreted on the image depends on its geological setting. Where both a right-looking and a left-looking radar image exist, the two can be compared, and the two kinds of deposit can be told apart. Dunes have regularly repeating sides with different slopes. These reflect radar waves with different strength in the two directions. A flat-lying deposit should look the same on radar images taken from any direction.
If this material is easily eroded, it points to fairly recent volcanic activity.
