The zone where land meets sea is known as the coast and the part between the lowest spring tides and the upper limit reached by splashing waves is the shore. A beach is the accumulation of sand or shingle on the shore. A headland is a point of land jutting out into the sea and a larger promontory is known as a cape. The indentation of a coastline, especially between two headlands, is a bay, a small bay with a narrow inlet is a cove and a large bay may be referred to as a gulf. Coastlines are influenced by a number of factors including the strength of the waves arriving on the shore, the gradient of the land margin, the composition and hardness of the coastal rock, the inclination of the off-shore slope and the changes of the level of the land due to local uplift or submergence. Normally, waves roll towards the shore at the rate of six to eight per minute and these are known as constructive waves as they tend to move material up the beach and have little erosive effect. Storm waves arrive on shore in rapid succession and are known as destructive waves as the swash moves beach material seawards. Under their influence, the sand and shingle on the beach is ground together and abraded. Around high tide, the power of a storm wave impacting on the foot of a cliff has a shattering effect as air in cracks and crevices is compressed and then expands rapidly with release of pressure. At the same time, sand and pebbles have an erosive effect as they are thrown against the rocks. This tends to undercut the cliff, and normal weathering processes such as the action of frost follows, causing further destruction. Gradually, a wave-cut platform develops at the foot of the cliff and this has a protective effect, reducing further wave-erosion.