The majority of the Isle of Man is made
up of rocks collectively known as the Manx Group.
The Manx Group was deposited as sediments on the floor of theIapetus Oceanaround490-470 million years
ago.
For the majority of the time the ocean floor would
have been very quiet with only a gentle rain of mud particles and
plankton. However, approximately every hundred or so years this stillness
would be interrupted by an avalanche of sediment. Known as turbidity
currents, these avalanches originate on the continental shelf and
are often triggered by earthquakes. They flow down submarine canyons
at speeds of around 20 metres per second. As they slow down, the sand
and mud they were carrying is deposited to form a new layer on the
sea bed. Over many thousands of years, these flows build up layer
upon layer of sediment into a giant pancake-shaped body known as a
submarine fan. Preserved within the Manx Group are several submarine
fans shown with yellow, orange and pale green colours on the central
map.
Diagram redrafted from Moore, D G 1969. Reflection
profiling studies of the California continental borderland: Structure
and quaternary turbite Basins. Geological Society of America
Special Papers, 107, 1-142
