Ayrshire's Gem EarthCache

Parking Pull-Off Area is available using the Waypoint listed.

South Aryshire’s Gem sits in the Firth of Clyde approximately ten miles from Girvan between Ireland and Scotland. Named Ailsa Craig, this volcanic plug from an extinct volcano that formed approximately 500 million years ago, has an interesting history. In the 16^th century it was used as a defense against Spanish invaders. In the 18-19^th centuries its use was a prison. Starting in the 19^th century the volcanic island was mined for rare granite, the only place in the world where Ailsa Craig Common Green Granite, Ailsa Craig Blue Hone Granite and Ailsa Craig Red Hone Granite are found, used for the production of all curling stones. Today, it continues to be a privately owned bird sanctuary.

We created an Earthcache here because as we stood admiring Ailsa Craig it was mind-boggling to imagine the height of this ancient volcanic plug's ORIGINAL volcano! And the more we researched about Ailsa Craig...the more we learned.

At the posted coordinates on the beach at the boulders please answer the following questions:

(and contact the CO using the link under the cache title ~ your answers will be accepted via Email or the Message Centre)

1) Describe the texture and appearance of the white vein layers in the rock compared to the large black boulders that they are embedded within. (size, feel, look, colour, area, shape, thickness, width, etc.)

2) Is there a difference in hardness between the white veins and the black boulders? Explain why you come to your conclusion.

3) Why do you think the beach is made of mostly modified basalt rocks and not granite rocks?

Those who send answers will receive a bonus.

Photos of you in the area are always nice to see and add to the interest of the geocache page. Please consider adding some of your own.
Favourite: If you like this Earthcache, please consider giving it a favourite point so others will know you enjoyed the experience. Thanks a bunch for visiting ~ hope you had fun.

Ailsa Craig

How Volcanoes are Formed

The earth’s crust is made up of broken plates called tectonic plates. These plates are floating on magma, hot liquid rocks, at the earth’s center. When the plates continuously very slowly move and rub against one another, some magma gets pushed up through the cracks in the rock. This continuous action creates volcanoes.

The word volcano in Italian means burning mountain. Vulcan is the Roman god of fire.

When a volcano erupts it is because the trapped material, the buildup of molten rock, ash, hard rock and gases are violently thrown into the air via pressure creating a hole in the earth’s surface. Some volcanoes are not quite as violent and end up leaking, rather than throwing, magma (known as lava once it has been exposed) more gently like pouring it from a cup.

Types of Volcanoes

Cinder cones: smaller volcanoes with steep sides. They have a single vent at the top usually within a bowl-shaped crater that blows blobs of lava and hot grainy rock high into the air. This lava breaks up into small fragments that cool, harden into cinders and fall back down around the vent forming a cone shape. They usually only erupt once and are smaller than 1,000 feet high.

Shield Volcanoes have wide low slopes and large craters at their summits. They usually emit wide thin flows of lava into all directions from the central vent rather than explosive eruptions. They end up shaped like a wide shield after the accumulation of layers of lava.

Lava Domes often grow inside the crates of composite volcanoes. Thick sticky masses of lava pour out and harden around the vents creating a dome, mostly increasing from within.

Composite Volcanoes (Stratovolcanoes) like Ailsa Craig are tall steep sided cones with a crater at the top. These volcanoes build up taller and taller after many eruptions as the lava can flow out of cracks in the cone’s wall and builds upon layers of ash and cinders. These fissures end up getting filled with hardened lava forming dikes that strengthen the volcano. These volcanoes have the most pressure build up creating the most violent eruptions. These are the tallest volcanoes and can reach over 8,000 feet tall. Eruptions blow out molten lava, basalt rocks, steam, ash and gaseous sulphur compounds.

Volcanic Plug Diagram

Volcanic Plugs

A Volcanic plug is also referred to as a volcanic neck or lava neck. Once a Stratovolcano becomes dormant erosion by wind and water destroys the external cone. This leaves exposed a volcanic plug - the hard-filled conduit and dikes that was once inside the volcano.

The Formation of Igneous Rocks

Rocks in the earth, deep inside the mantle, are under a constant change of high pressure and high temperatures causing them to melt. Others are in a semi-liquid state. Melted liquid rock is called magma. When magma is exposed on the surface of the earth it is called lava or molten rock. Igneous in Latin means fire-formed.

The rock in a volcanic plug is hard igneous rock meaning the rock has formed from the solidification of magma or lava. When magma cools into solid rock then crystals are formed. There are different kinds of igneous rock depending on the rate the solid rock had cooled, where it cooled, and the differences in the chemical compositions.

Granite is one of these results and is the material make-up of Ailsa Craig's volcanic plug. It is an intrusive igneous rock that formed when the rock cools slowly while still under the surface of the volcano. Variations in rock will be the result of different temperature, compositions and crystal content when formation occurs. Visually granite has large coarse-grained mineral crystal specks of different colours depending on the minerals that were trapped inside when the rock was formed. This hard granite plug is all that is left of the extinct volcano after much of the exterior volcano (softer rock and soil) has been eroded away.

Basalt rock is an extrusive rock (rapid cooling) that forms when basaltic lava is exposed at or very near the surface but it can also form inside small intrusive (slow cooling) bodies. It has a very fine-grained mineral texture (or even invisible crystals) due to the molten rock cooling too quickly for large mineral crystals to grow. Basalt is usually dark from the iron and magnesium elements in it or it can be lighter due to the magma containing more silica and aluminum in it or red due to oxidation.

Quartz is a common mineral found in other rocks that can range is a variety of colours: citrine, rose quartz, amethyst, smoky quartz, milky quartz, etc.

CedarNCo have earned (GSA) Geological Society of America's highest earthcache level:

Platimum Earthcache Level is awarded by Geo Society .org for visiting and logging 20 or more EarthCaches in 5 or more states/provinces/countries and have created 3 or more EarthCaches.