Marsden Rock

During the Carboniferous Period, the Marsden coast was part of a continent and tropical swampland which stretched across the equator. Over time, the peat, sand and mud hardened to form the coal measures and the land drifted north of the equator. This land became a desert and subsequently lay below sea level, flooded around 260 million years ago by the Zechstein Sea which periodically rose and fell.^[1] The Permian Magnesian rocks found on Marsden coast were formed around 250 million years ago.^[2] The land continued to drift northwards over the next 250 million years until it reached its current position. The ice age which occurred around 15,000 years ago was largely responsible for shaping the current landscape of the Marsden coastline and surrounding area.^[1]

The Magnesian Limestone coast along Tyne and Wear is variable; some sections are firm and compact whilst other sections are brittle and easily disintegrated by the sea and weather. Marsden Rock was formed by erosion of less-resistant stone along the joints of the cliffs of Marsden Bay, resulting in an isolated stack of compacted limestone.^[3][4] A channel was carved through the rock by waves which formed a natural arch.^[5] By the 1800s, the arch had become large enough for sailing boats to pass through at high tide.^[6] Small caves have been carved into the rock over time which can be observed at low tide.^[7] Resistant beds, jutting out from the cliff and covered in vegetation, and promontories have also developed around the rock.^[8] The surrounding beach is composed of sand and gravel generated by shoreward drifting of sediment.^[9]

Marsden Rock has eroded and had various collapses throughout its history. In 1865, part of the rock gave way and five tons of rock fell through a building below.^[10] In early 1996 following a winter of storms, the top of the natural arch collapsed.^[11] This caused the rock to split into two separate stacks.^[12] The smaller of these two stacks, standing at 33 metres (108 ft),^[13] was inspected and deemed unstable and in danger of collapsing. It was demolished by the National Trust in 1997 in the interest of public safety.^[12][14] The remaining stack stands at 90 feet (27 m) high.^[15]

In 2018, it was reported that the materials forming the cliffs near Marsden Rock were weak and highly prone to fragmentation, with continued evidence of weathering.^[16] In 2020, the Rock itself was reported as "broadly stable", but local collapses of cave formations were still possible.^[7]

• 
  Picture taken in 2006 of a smaller arch which has been carved out of the remaining magnesian limestone stack.
• 
  Marsden Rock in 2011, 14 years after the collapse of the arch and subsequent demolition of the smaller stack.

The limestone cliffs which surround Marsden Rock are among the most important breeding colonies for seabirds in the north east of England.^[17] In the summer, the cliffs by Marsden Rock are home to fulmars, cormorants, kittiwakes, herring gulls, and razorbills.^[15] The rock itself is an important habitat for cormorants, which have been there since 1960 but have never been seen to breed. Puffin and guillemot fly past the area regularly and terns feed offshore. In the late autumn, migrant terns, skuas, and gannets can be seen on the rock. Peregrine falcons can occasionally be found in the winter along with Lapland bunting and snow bunting.^[18][19][17] In 1998, it was reported that Marsden Rock was the site of the only recorded breeding ground for Manx shearwater on the east coast on mainland Britain.^[20]