1. Volcanic plugs
Volcanic plugs are formed when magma inside the vent of an active volcano hardens. Erosion by glaciers can result in "crag and tails" where the plug is exposed on one side and a long slope of material is left on the other side. Further erosion may remove the rock that surrounds the plug while plug itself remains resistant to erosion - this creates distinctve upstanding structures in the landscape.
2. Glacial Features
12,500 years ago the landscape in front of you was covered by a glacier. From the Ochils, glaciers stretched east, forming Loch Leven underneath them - by eroding away the bedrock to form a shallow depression. At the end of ice age, the glaciers retreated, filling the whole area with deposits of sand and gravel. The River Leven wove through these sediments, causing the the loch to dam to the east and susequently flood.
3. Raised Peat Bog
Raised bogs are areas of deep, wet peat and Portmoak Moss is one of the few surviving raised bogs in central Scotland. Most of the site was drained and worked for peat in the past, but the centre of the original peat dome remains intact, with samples suggesting depths of peat up to 6m. In the 1960s further drainage took place and conifers were planted, some of which became windblown by the late 90's. The Woodland Trust acquired the site in the mid 90's and cleared an area of windblow on the raised area, intending to leave the area to natural succession. However, remnants of raised bog communities were found underneath the trees including a number sphagnum mosses. It was decided to attempt a restoration of the intact peat dome back to a functioning lowland raised bog ecosystem.
4. The Sleeping Giant
Directly across from you lies Benarty Hill: "The Sleeping Giant" - a long ridge whose northern and western slopes lie in Tayside, the southern and eastern in Fife. The lower slopes are steep on all sides, but the summit is relatively flat. Benarty Hill is 356m high - making it a Marilyn. Its steep slopes are part of the Midland Valley Sill. Sills are formed when magma (molten rock) is injected between layers of existing rock. 305 million years ago, a mass of magma originating near Norway, forced its way through solid layers of rock all the way to Central Scotland where it cooled into a huge underground structure - the Midland Valley Sill - up to 150 metres thick and over 1,600 square km in area. Erosion, particularly round the edges, has exposed the sill - such as can be seen here.
Look at the information board here at the co-ordinates. Answer the questions below which are based on the four points of geological interest above. Please email your answers to myself - do not include them in your log.
1. (a) How many volcanic plugs are mentioned in the "What can you see?" paragraph? And what are their names?
(b) Which geological age are they relics from?
2. How does the explantion for the formation of Loch Leven on the information board differ from that given above in the cache description?
3.Use the map on the board to Identify Portmoak Moss below. You can see the border of conifers that surrounds the cleared area of peat bog. Estimate the size of the exposed area of bog.
4. (a) Which rock is mentioned in relation to "The Sleeping Giant"?
(b) Where on the hill is this found?