What type of rock is giants causeway

What caused this is actually not so unique to this windy coast of Northern Ireland. It is a common feature when a hot, mafic basalt or dolerite volcanic rock either lava at the surface or shallow magma just below the surface cools and contracts into a hexagonal columns e.

The rapidly cooling lava cools from the outside toward the centre which causes contractions, and differences in the way it cools leads to the formation of hexagonal, prismatic column shapes termed columnar jointing.

Relatively new studies have deciphered more of the science on how these columns formed. It has also been worked out recently by computer models and physics as to why the columns take on the hexagonal form Hofmann et al. It cools and takes the shape of the hexagon, and then the lava around also cools and tends to form around more hexagonal shapes. The region consisted of chalk sedimentary beds which were then subjected to volcanic activity, forming a lake of lava that cooled relatively rapidly, forming the shapes we see now.

Another version of the story goes back to an old folk tale involving an Irish giant named Finn McCool. According to the tale, Mr. McCool built the crossing from Northern Ireland to Scotland by throwing boulders in the sea in order to bring his Scottish girlfriend over and confront his Scottish rival. For example, Tasmania has many amazing exposures of columnar dolerite, such as seen at Cape Hauy and Raoul. Iceland also hosts some spectacular basalt columns where cascading waterfalls makes for quite the photos.

Another filming site is the stunning Dunluce castle , situated at the edge of a prominent basalt outcrop. Thanks for reading! Email Address. Great stuff. However, the main causeway lavas are divided into an upper colonnade, a central entablature and a thick basal colonnade.

This is thought to be caused by water seeping into cracks as they were forming, accelerating cooling and disrupting large colonnade formation in the upper and middle sections. Following the outpouring and cooling of each of these lava flows, a period of inactivity allowed the topmost section of the basalt to be exposed to intense, persistent tropical weathering, forming a soil rich in iron and aluminium, called laterite.

Laterites form by the leaching of the parent rock during the wet season, the resulting solution is brought to the surface during the dry season and removed, progressively depleting the soil of easily dissolved ions such as sodium, potassium, calcium and magnesium, leaving behind the more insoluble elements such as aluminium and iron oxides.

Laterite formation occurs on the surfaces of the basalt that are in contact with water; on the surface and within cracks in the rock. These cycles are spectacularly displayed in the amphitheatre shaped cliffs in the image above, from the iconic stepping stones of the middle basalts, through the distinct red layer of the laterite and into the columns of the upper basalts.

About Visitor Centre Tours Contact. Geology Of The Giants Causeway. It is the iron oxides that give this soil its characteristic brick-red colour. Share this post. Share on facebook. Share on twitter.

Share on linkedin. Share on pinterest. Share on print. Share on email. But until now, geologists had been unsure of the threshold at which cooling magma suddenly fractures into a geometric pavement.

We have been wanting to know whether the temperature of the lava that causes the fractures was hot, warm or cold. The 20cm-long cylinders, gripped by a clamp at each end, were heated to more than 1,C until they began to soften into lava. The samples were fixed at each end in a mechanical grip and cooled to test at what point they snapped.