The line cuts again through the lip of the basin, and we are in the Crau.

At a remote period, but, nevertheless, in one geologically modern, the
vast floods of the diluvial age that flowed from the Alps brought down
incredible quantities of rolled stones, the detritus of the Alps. This
filled up a great bay now occupied by the mouths of the Rhone, and spread
in a triangle from Avignon as the apex, to Cette in the west, and Fos in
the east. This rubble, washed down from the Alps, forms the substratum
of the immense plain that inclines at a very slight angle into the
Mediterranean, and extends for a considerable distance below the sea. Not
only did the Rhone bring down these boulders, but also the Durance, which
enters the Rhone above Arles, and formed between the chain of Les Alpines
and the Luberon another triangular plain of rolled stones, with the apex at
Cavaillon and the base between Tarascon and Avignon. But the Durance did
more. There is a break in the chain on the south, between the limestone
Alpines and the sandstone Trevaresse; and the brimming Durance, unable to
discharge all her water, choked with rubble, into the Rhone, burst through
the open door or natural waste-pipe, by Salon, and carried a portion of her
pebbles into the sea directly, without asking her sister the Rhone to help
her. Now the two great plains formed by the delta of the Rhone, and that
of the Durance into the Rhone, are called the great and little Craus. They
were known to the ancients, and puzzled them not a little. Strabo says of
the Great Crau: "Between Marseilles and the mouth of the Rhone, at about a
hundred stadia from the sea, is a plain, circular in form, and a hundred
stadia in diameter, to which a singular event obtained for it the name of
the Field of Pebbles. It is, in fact, covered with pebbles, as big as the
fist, among which grows some grass in sufficient abundance to pasture herds
of oxen."