The beaches at Holderness are its main problem. Boulder clay erodes to produce mainly clay particles, which are easily transported out to sea, rather than accumulating close to the cliffs as beach sand. Although there are beaches, there is never enough sand to stop the waves reaching the cliff base at high tide. The beaches are narrow and offer little friction to absorb the wave energy and protect the cliffs. The sand that is produced is taken southwards by longshore drift, leaving the Holderness cliffs poorly protected against wave attack. Eventually, a small amount of beach material reaches the spit at Spurn Head, where it accumulates. This has been stopped at Mappleton, in Holderness because they have used groynes. These slow longshore drift because they just get in the way. So it stops most of the sediment, which then just stay there and accumulates. Only some passes, but gets stuck on another groyne and only a small amount of sediment passes that. But this doesn’t help the coast further south because it means less sediment is deposited there. So there is hardly a beach and more erosion can occur.
Also cliff-erosion processes occur. There are two types of processes that are involved in the rapid erosion of the clay cliffs on the Holderness Coast. These are Cliff-foot erosion, which is caused by wave action at the base of the cliff, and sub-aerial processes, which affect the cliff face. In cliff-foot erosion the waves attack the base of the cliff, eroding the cliff foot. Abrasion or corrasion occurs, where the waves advance, picking up sand and pebbles from the seabed. As they break, the material is hurled at the cliff, chipping away at the base. Hydraulic action also happens, when the advancing waves trap air inside cracks in the cliff, increasing air pressure. As the wave retreats, the air explodes, weakening joints and cracks causing pieces of rock to break away. Also Corrosion can occur. This is where the cliffs are formed from alkalis such as chalk or limestone, or an alkali cement bonds the particles together and solution by weak acids in sea water dissolves them. Each process causes the cliff to become undercut and unstable, leading to collapse.
When exposed, the cliff face is affected by two sets of sub-aerial processes. One of them is weathering, which breaks down the solid rock fragments into smaller fragments or dissolves them chemically and there are three types of weathering. The second process is mass movement, which is the movement of fine weathered material downslope by gravity. All three types of weathering processes affect the Holderness cliffs. One of them is Physical weathering, including any kind of mechanical action. The best example along this coast is freeze-thaw. Water enters cracks when it rains and freezes during cold weather. Freezing water expands in volume by 10%, putting pressure on the rock and enlarging the crack. If this is repeated many times, the crack enlarges and eventually fragments of boulder clay fall from the cliff face. The second type is biological weathering. As seedlings germinate, fine root hairs find their way into microscopic cracks in the rock. As the roots grow, they prise the cracks apart and enlarge them. Fully grown plants can be seen growing out of solid rock, and their roots break the rock up. Once the plant ies, the rocks fall apart. Thirdly is Chemical weathering. Here rainwater combines with CO2 in the atmosphere to form a weak carbonic acid, or with SO2 to form sulphurous acid. These acids dissolve the alkali chalk at Flamborough Head, weakening it, but chemical weathering is less important than physical or biological weathering along the Holderness coast.
Mass movement processes occur on the Holderness coast. Slumping is the main form of mass movement affecting the clay cliffs along the Holderness coast. Alternate wetting and drying of the clay causes it to expand when wet and shrink when dry. This causes cracks to form, especially during long dry periods. The next time it rains, water rapidly enters the cliffs and percolates into the cliff. The clay then becomes lubricated or slippery, and gains extra weight. As a result, the cliff cannot support the heavier clay and gravity leads the clay to slide downslope. This movement is known as slumping, or landslip. The slumped material collects at the base of the cliff, and is then washed away by the sea.
All of these factors cause erosion by themselves, but they all affect the Holderness coast practically at the same time, which leads to a rapid erosion of the cliffs and the coast, and the fairly weak rock types don’t help either.