Location

Spurn Head spit is located at the mouth of the Humber estuary on the Holderness coast in Yorkshire, North-east England.

What is a spit?

A spit is an area of sand or shingle which either extends at a gentle angle out to sea or which grows across a river estuary. Many spits are characterised by a hooked, or curved end. Spits develop in places where:

• Longshore drift moves large amounts of material along the beach
• There is a sudden change in the direction of the coastline
• The sea is relatively shallow and becomes progressively more sheltered.

How was Spurn Head spit formed?

Geological influences

• The coastline to the north of Spurn Head is made of incoherent, soft boulder clay. This boulder clay or till was left as glacial deposits during the last ice age. As a result, it is extremely susceptible to sub-ariel and marine erosion

Waves

• Sand and shingle eroded from the cliffs updrift of Spurn Head is carried south through longshore drift.
• As the coastline changes direction as it meets the Humber estuary, the sediment is deposited at the river mouth. The sea is no longer able to carry the sediment due to the change of direction and the reduction of wave energy due to the impact of the river water entering the sea.

Wind

• Occasionally. Strong winds will blow from a different direction. Consequently, the waves will approach from a different direction. Some material will be pushed inland, causing the end of the spit to curve.
• When the wind returns to it's usual direction, the spit will continue to grow southwards, developing further hooked ends during times of changed wind direction.

Other factors

• The spit cannot grow cannot grow across the Humber estuary due to the speed of the river carrying material out to sea.
• The spit became permanent when the prevailing winds picked up sand and blew it inland to form sand dunes. Later, groynes were built to make the spit more stable.
• The salt marsh developed behind the spit in the sheltered water. As the river water gets caught behind the spit, the velocity decreases causing material being transported downstream to be deposited behind the spit.

D. Drake 2010