Drakes Island EarthCache
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DRAKES ISLAND IS PRIVATE LAND AND IS NOT OPEN TO THE PUBLIC AT ANY TIME.
Three thousand years ago Drakes Island was connected to the Cornish main land. Look at the area between Drakes Island and the Cornish coast and explain two reasons why you think that Drakes Island is no longer attached to the main land. If possible please take a photo of yourself or your GPS with Drakes Island in the back ground and put this on your log (the photograph is not compulsory to log this find). Please email your answers to us through our profile. You are then free to log your find, finds without an email will be deleted so please do not log until you can email.
Drake's Island is a 6.5 acres (2.6 ha) island lying in Plymouth Sound, the stretch of water south of the city of Plymouth, Devon, England. The rocks which make up the island are volcanic tuff and lava, together with marine limestone of the mid- Devonian period.
Tuff (from the Italian tufo) is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. Tuff is sometimes called tufa, particularly when used as construction material, although tufa also refers to a quite different rock. Rock that contains greater than 50% tuff is considered tuffaceous.
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at temperatures from 700 to 1,200 °C (1,292 to 2,192 °F). Up to 100,000 times as viscous as water, lava can flow great distances before cooling and solidifying because of its thixotropic and shear thinning properties.
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3). Many limestone’s are composed from skeletal fragments of marine organisms such as coral or foraminifera. Limestone makes up about 10% of the total volume of all sedimentary rocks. The solubility of limestone in water and weak acid solutions leads to karst landscapes, in which water erodes the limestone over thousands to millions of years. Most cave systems are through limestone bedrock. Limestone has numerous uses: as a building material, as aggregate for the base of roads, as white pigment or filler in products such as toothpaste or paints and as a chemical feedstock.
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya (million years ago), to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya (ICS, 2004). It is named after Devon, England, where rocks from this period were first studied. The Devonian period experienced the first significant adaptive radiation of terrestrial life. Since large vertebrate terrestrial herbivores had not yet appeared, free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents. By the middle of the Devonian several groups of plants had evolved leaves and true roots.
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