Washed out 'A' horizon - so leached it is grey in colour

Large zone of eluviation (Washed out layer).

 Very heavy leaching

Deeper layers are darker as minerals are reprecipitated lower down.

Zone of illuviation (B)  ('washed in' layer)

May be an iron pan - so many iron minerals collected that it impedes drainage.

Typical of Upland Britain on  Moorland or under Coniferous Forests.