27 SEPTEMBER 2008, Page 28

The speed of lava

Sir: In his review of Mary Beard’s Pompeii (Books, 20 September), Raymond Carr is incorrect to describe ‘a burning lava, flowing at great speed’. To the best of my knowledge, this would in fact have been a pyroclastic flow, derived from the Greek, which literally translates to ‘broken fire’. This is a cloud of superheated toxic gas and small rocks — the temperature can reach 1,000˚C. Lava does not travel in such a manner.

Andrew Stibbard

London SW9