Fossil Crocodile, Lisbon Natural History Museum. Photo: Luis Lima |
This specimen is housed in the Geological Museum of Lisbon. The museum was built in 1857 and is home to beautiful paleontology, archaeology and mineral specimens.
Fossil Crocodile, Lisbon Natural History Museum. Photo: Luis Lima |
Hoplites maritimus / Hoplites rudis |
Hoplites sp. from the Early Cretaceous of Dorset, UK |
Hoplites dentalus, from Albian deposits near Troyes, France |
Agriotherium / Short-Faced Bear |
Landmannalaugar is at the northern tip of the Laugavegur hiking trail that leads through natural geothermal hot springs and an austere yet poetically beautiful landscape.
Here, you can see the Northern Lights play through the darkness of a night sky without light pollution and bask in the raw geology of this rugged land.
The Fjallabak region takes its name from the numerous wild and rugged mountains with deeply incised valleys, which are found there. The topography of the Torfajokull, a central volcano found within the Fjallabak Nature Reserve, is a direct result of the region being the largest rhyolite area in Iceland and the largest geothermal area (after Grimsvotn in Vatnajokull).
The Torfajokull central volcano is an active volcanic system but is now in a declining fumarolic stage as exemplified by numerous fumaroles and hot springs. The hot pools at Landmannalaugar are but one of many manifestations of geothermal activity in the area, which also tends to alter the minerals in the rocks, causing the beautiful colour variations from red and yellow to blue and green, a good example being Brennisteinsalda. Geologists believe that the Torfajokull central volcano is a caldera, the rim being Haalda, Suðurnamur, Norður-Barmur, Torfajokull, Kaldaklofsfjoll and Ljosartungur.
The bedrock of the Fjallabak Nature Reserve dates back 8-10 million years. At that time the area was on the Reykjanes – Langjokull ridge rift zone. The volcano has been most productive during the last 2 million years, that is during the last Ice Age Interglacial rhyolite lava (Brandsgil) and sub-glacial rhyolite (erupted under ice/water, examples being Blahnukur and Brennisteinsalda are characteristic formations in the area. To the north of the Torfajokull region sub-glacial volcanic activity produced the hyaloclastites (moberg) mountains, such as Lodmundur and Mogilshofdar.
Volcanic activity in recent times (last 10.000 years) has been restricted to a few northeast – southwest fissures, the most recent one, the Veidivotn fissure from 1480, formed Laugahraun (by the hut at Landmannalaugar), Namshraun, Nordurnamshraun, Ljotipollur and other craters which extend 30 km, further to the north Eruptions in the area tend to be explosive and occur every 500 – 800 years, previous known eruptions being around A. D 150 and 900.
Sea jellies and jellyfish are the common names for the medusa-phase or adult phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria — more closely related to anemones and corals.
Jellyfish are not fish at all. Jellyfish evolved millions of years before true fish.
The oldest conulariid scyphozoans — picture an ice-cream cone with fourfold symmetry — appeared between 635 and 577 million years ago in the Neoproterozoic of the Lantian Formation a 150-meter-thick sequence of rocks deposited in southern China.
Others are found in the youngest Ediacaran rocks of the Tamengo Formation of Brazil, c. 505 mya, through to the Triassic. Cubozoans and hydrozoans appeared in the Cambrian of the Marjum Formation in Utah, USA, c. 540 mya. Like other soft-bodied organisms, ctenophores (comb jellies), sea jellies and jellyfish only produce fossils only under exceptional taphonomic conditions — think rare.
I have seen all sorts of their brethren growing up on the west coast of Canada. I have seen them in tide pools, washed up on the beach and swam amongst thousands of Moon Jellyfish while scuba diving in the Salish Sea. Their movement in the water is marvellous.
In the Kwak̓wala language of the Kwakiutl or Kwakwaka'wakw, speakers of Kwak'wala, of the Pacific Northwest, jellyfish are known as ǥaǥisama.The watercolour ǥaǥisama you see here is a bit of fancy. While I chose blue, purple and pink for these lovelies, they also come in bright yellow, orange and relatively clear — and are often luminescent.
Jellyfish such as comb jellies produce bright flashes to startle a predator, others such as siphonophores can produce a chain of light or release thousands of glowing particles into the water as a mimic of small plankton to confuse the predator.
For most jellyfish bioluminescence is used for defence against predators — and about half of all jellyfish are bioluminescent. Some produce a glowing sticky slime that clings to predators making them vulnerable to other predators. Some jellyfish can release their tentacles as glowing decoys. So you see that there are many strategies for using bioluminescence by jellyfish.
All bioluminescence comes from energy released from a chemical reaction. This is very different from other sources of light, such as from the sun or a light bulb, where the energy comes from heat. In a luminescent reaction, two types of chemicals, called luciferin and luciferase, combine together. The luciferase acts as an enzyme, allowing the luciferin to release energy as it is oxidized. The colour of the light depends on the chemical structures of the chemicals.
There are more than a dozen known chemical luminescent systems, indicating that bioluminescence evolved independently in different groups of organisms. One type of luciferin is called coelenterazine, found in jellyfish, shrimp, and fish. Dinoflagellates and krill share another class of unique luciferins, while ostracods (firefleas) and some fish have a completely different luciferin. The occurrence of identical luciferins for different types of organisms suggests a dietary source for some groups. Organisms such as bacteria and fireflies have unique luminescent chemistries. In many other groups, the chemistry is still unknown
Some of the most amazing deep-sea jellyfish are the comb jellies, which can get as large as a basketball, and are in some cases so fragile that they are almost impossible to collect intact.
Also spectacular are the siphonophores, some of which can reach several meters in length. Siphonophores deploy many tentacles like a gill net casting for small fish.