Visiting York recently, some of the buildings here are hundreds of years old - sometimes nearly a thousand - and as such, many are showing their age. I walked past the Theatre Royal and spotted several different types of weathering happening here.
You'll need to look at the front of the building here - look up and along the building and around the corner to the right and see what you can find. Use the information on the different types of weathering to help answer the questions.
1) Standing looking at the right of the entrance, on either side of the large glass windows, just above head heaight, there are six carved heads. Number them 1 (nearest the entrance, on the left), to 6 (furthest to the right).
a) Which displays the most signs of chemical weathering?
b) Why are carved statues particularly good at showing signs of chemical weathering
c) Do you think the theatre's location by a busy road accelerates the weathering here?
2) Describe one sign of physical weathering you can spot
3) Describe one sign of biological weathering you can spot
4) Take a photo of yourself at GZ, or an identifying item, being careful not to reveal any of the answers to the questions.
Please submit your answers via message though the Geocaching website or by sending me an email - there is no need to wait for a response before logging your find.
Weathers Effect on Rocks
Weathering is exactly that - the effect the wind and rain has on rocks. Rain can permeate rocks where the particles are loosely packed together, washing grains away. The repetition of this over time can be seen on the surface of the stone, the type of stone and the location it is placed in affect the speed this takes place.
Often in statues or carvings, one of the effects of weathering can be seen where the carvings are - what started out when the statue was new as a sharp edge becomes softer as the grains of the fine, sharp edge are removed by weather - think of a drawing with a blunt rather than a sharp pencil. Sometimes the stone can become stained by other chemicals in the air or water.
Whole sections can break off by strong wind or by water entering gaps, freezing and expanding, causing gaps to get wider and wider and eventually break over time.
More information on the various types of weather is below.
Types of weathering
Physical
Caused by changing temperature. Temperature causes rock to expand and contract as it gets warmer and colder. Repetition of this action can cause cracks and breaks. Freeze-thaw weathering also affects sandstone. When water seeps into the pores of sandstone and freezes during cold weather, it expands, exerting pressure on the rock. This expansion can cause the sandstone to crack and fragment over time. When the ice thaws, the water contracts, further stressing the rock. Over many freeze-thaw cycles, this gradual weakening and fragmentation can lead to the disintegration of sandstone into smaller pieces. Soot from factories can also contribute to physical weathering by abrading rock surfaces.
Chemical
Chemical weathering significantly affects sandstone. Car exhaust fumes contain nitrogen oxides and sulfur dioxide, which form nitric and sulfuric acids in the atmosphere, leading to acid rain. This acid rain dissolves minerals in sandstone, weakening it. For statues, acid rain erodes the surface, dissolving the stone and causing the loss of fine details, blurring carvings, and degrading facial features over time.
Chemical weathering also occurs naturally when carbon dioxide in the atmosphere dissolves in rainwater, forming carbonic acid which can then dissolve minerals in rocks like sandstone.
Biological
Biological weathering involves the breakdown of sandstone by living organisms. One common mechanism is root wedging, where plant roots grow into cracks and crevices of the rock. As the roots expand, they exert pressure, causing the rock to fragment over time. Organisms such as lichens and mosses can release acids that chemically weather the minerals in sandstone.