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involved material up to the size of cobbles,
which need very high velocities (>100m/sec)
for movement. Horizontally flowing water
of such velocity is usually associated with
powerful rivers and it is difficult to
envisage how it can be associated with
creating a landform about 250m across.
The textbook explanation is obviously
inadequate in this case. A possible
explanation could be that the sands and
gravels were formerly more extensive and
that the mounds represent the final stages
in the erosion of the deposits.
The final visit was to Wiveton Downs
(TG 030422), also known as the Blakeney
Esker. From the picnic site, good views
were obtained, showing the landform to be a
long, angular ridge Such ridges are
formed by waters flowing through or under the
ice. in tunnels or crevasses, building up a
sand and gravel bed confined by ice walls,
so that when the ice melts, the materials
are left upstanding, forming a ridge.
Sections in the ridge show that a wide range
of materials were deposited, from gravels,
indicating very high energy flow, to sands
or even silts, laid down during quieter flow.
Some of the gravels lacked bedding structures,
which is taken to indicate deposition in a
tunnel. These deposits were seen to be
laid down upon till (boulder clay), deposited
directly from the ice.
During the day, a variety of landforms was
seen and exposures allowed the internal
structures to be examined. In most cases,
the landforms and sediments complement one
another and illustrate well the normal text-
book explanations of their origin, but in