Saturday, July 28, 2007

Brownsea Island

An Island within Poole harbour, Dorset. This is the place where the scouting movement was born out of an idea by Lord Baden-Powell. The scouting movement is just about to celebrate the 100th anniversary of the very first camp held here in 1907!

Wednesday, July 18, 2007


Of all the fossils associated with the Jurassic Coast, the ammonite is probably the most well known. They appeared at the beginning of the Jurassic period around 200 million years ago. They are cephalopod molluscs related to the octopus and squid, although thier closest living relative is the nautilus (seen below).

Ammonites were free swimming creatures, that used the chambers in thier shells as ballast tanks to control bouancy. The soft parts of the animal itself were located in the end chamber. Judging by the number of fossils we now find, they must have been a common sight floating around the Jurassic and Cretatious seas in various shapes and sizes

Despite being common, ammonites are very special fossils, of enormous use to geologists trying to work out the history of ancient times. Ammonites evolved very quickly and so are important in helping to identify rocks as being from a particular age. To understand this, is so important, to remember that the type of rock that forms depends on its geopgraphical location. Different sediments are now forming in the English Channel and North Sea. In millions of years time, after these sediments have compacted to form rocks, they may look totally different. It may be that the skeletal remains of cod, plaice and herrings etc will confirm that they originated at around the same time. However if all these fish survive for millions of years, it may not help the geologists of the future at all

Ammonites are valuable becUAE Individual species did not last long before they evolved into different species. When we find them in two different rocks therefore, they tell us that those rocks are of the same age. For example, the ammonite Titanites, seen in many garden walls on the Isle of Purbeck, lived at the time when the Portland rocks were being deposited. Find an example of Titnates in a rock and you know how old that rock is

What makes ammonites even more fascinating to the amateur geologist is that the evolutionary trends are relatively easy to pick out. It seems that as ammonites evolved they developed more and more ornamentation on the outside of thier shells, so generally speaking the ones with smooth shells are earlier that those with spikes and nobbly bits on. Another trend involved the walls that seperated the chambers in the ammonite shell. These gradually became more and more elaborate and form beautifully intricate patterns on the outside where the shell has worn away

At the end of the Creatateous (around 60 million years ago), the ammonites, like the dinosaurs, mysteriously dissapear. By that time they had gone into evolutionary reverse, with some forms beginning to uncoil, eventually resulting in forms that were almost straight

The Jurassic seas, where much of Dorset originated, must have once swarmed with these beautifull creatures with thier elaborate ornamentation and possibly vibrant colours. They proliferated in rich, tropical seas, and due to thier free-swimming lifestyle have left thier imprint in a variety of rocks


Graphics: Wikipaedia
Text: Fossils and Rocks of the Jurassic Coast by Robert Westwood

Friday, July 13, 2007

Slightly to the West of Durdle Door

To find this particular rock which is from the Cretateos (around 65 million years ago) period, head for Durdle Door, to the East of Lulworth Cove. If you follow the path to Durdle Door, you will see this rock formation from the path

Sunday, July 08, 2007

Longbarrow, Charmouth

Sunday, July 01, 2007

Dinosaurs on the Jurassic Coast

About 225 million years ago, the first dinosaur appeared in the forests of what is now South America. It was a small two-legged animal about the size of a chicken. It was quick and agile on its two strong legs, and probably a very effective hunter. Within about 30 million years its dinosaur relatives had become the dominant creatures on the planet; they were to reign for about 165 million years

Most people know the dinosaur is a reptile, but many erroneously think the term applies to all giant reptiles. In fact dinosaurs came in all shapes and sizes; but certainly some of the larger ones were the biggest, fastest and most ferocious animals that have ever walked the Earth. The main distinguishing feature of a dinosaur is that it is a reptile that developed an upright gait. This gave it an immediate advantage over other reptiles with thier awkward sideways gait

At the beginning of the Triassic period there was a mass extinction of many species. These events have happened a number of times during geological history and have continued to puzzle geologists. Certainly much competion to the emerging dinosaurs was removed by this global catasrophe. The dinosaurs diversified rapidly during the Triassic and, with little competition, got bigger and bigger. Other reptiles also evolved, some taking to the air

During the Jurassic dinosaurs diversified further and became truly dominant. Huge plant eating varieties evolved along with ferocious predators. Other forms of life also flourished and, in the sea, other reptiles grew to immense size. The shallow, tropical seas in which Dorset's rocks were deposited must have been home to a fantastic array of life

The Cretatious period saw dinosaurs continue to dominate. Some of the most well known dinosaurs like Tyrannosaurus lived in this period and the shallow lagoons where the Purbeck rock was formed have helped preserve thier bones for us to study. At Durlston Bay and Worbarrow Bay it is possible to sea the footprints of these massive creatures. The most likely example you will find is the three pronged footprint of the Iguanadon (pictured above), a plant eater that was up to 10 metres long and 5 metres high. At the end of the Cretatious period (about 65 million years ago) the dinosaurs died out.

Whether or not it was the impact of a huge meteorite as has been suggested is still open to debate. The evidence is strong, but it should be remembered that mass extinctions have taken place at other times


Text: Fossils and Rocks of the Jurrasic Coast by Robert Westwood
Graphic: Wikipaedia