Monthly Archives: November 2019

Coloured Lakes?

Environmental Geology

It is difficult to believe that Lakes can be coloured if you have not seen them. In Kenya, there are lakes with different colours. Here are some of the examples:

1. Lake Turkana – The Jade Sea

Lake Turkana is famous for its Turquoise colour hence it’s nickname, The Jade Sea. It is the largest Alkaline lake in the World and also the largest permanent Desert Lake in the World. Lake Turkana is also the Largest lake in Kenya with an area of 50 km X 300 km since Lake Victoria is shared between Kenya, Uganda and Tanzania.

2. Lake Magadi

Located on the Southern Part of the Great Rift Valley, it has a bed made almost entirely of solid soda or semisolid soda. This lake turns pink during the algal blooms. It is near Lake Natron in Arusha, Tanzania, that also turns pink.

3. Lake in Kapedo

This lake forms a Bright Blood Red colour that has inspired some myths in the communities living around it. The lake is located at the Southern end of the Suguta Valley.

The colours of the Lakes above are due to Dunalliela algae, Dunalliela salina, that thrive in alkaline saline water of the Lakes above. The algae is green in colour when exposed to salinity but turns red in high salinity and light intensity. In these conditions, the algae produce protective carotenoids in their cells that are responsible for the bright colours in the Lakes.

Do you know of any other lake that is coloured? Let us know in the comments below.

Stromboli, The Lighthouse of the Mediterranean

Volcanicity and Igneous Activities
Stromboli, a small island north of Sicily, is one of the most active volcanoes in the world and famous for its normally small, but regular explosions throwing out glowing lava from several vents inside its summit crater. This activity has been going on for at least 2000 years, as long as there is written memory of the activity, which Stromboli lended its name to, the so-called strombolian activity.
The N-most island of the Eolian Islands is famous for its spectacular incandescent nighttime explosions, that have long attracted visitors from all over the world and brought the volcano the nickname the “Lighthouse of the Mediterranean.” Stromboli has even given its name to this kind of typical small explosions.
3af3ceb315For more information about Stromboli Stratovolcano, click: https://www.volcanodiscovery.com/stromboli.html

Cinnabar: An attractive but extremely toxic mineral

Mineralogy and Petrology

Cinnabar is a Mercury Sulphide mineral with a chemical formula HgS. It has a bright red colour and a Moh’s hardness of 2-2.5. Cinnabar was originally used as a pigment and cut into jewellery. However, due to its toxicity, these uses have been discontinued.

Cinnabar is a hydrothermal mineral precipitating from ascending hot waters through fissures and forms at low temperatures of less than 200 degree centigrade and at shallow depths. It is associated with Igneous Rocks.

Currently, Cinnabar is used an an ore of Mercury, where its powder is heated in a kiln and mercury vapour sublimes.

cinnabarMetacinnabar is a polymorph of cinnabar. It has the same chemical composition (HgS) as cinnabar but a different crystal structure. Cinnabar is trigonal, while metacinnabar is isometric. The two minerals should not be confused with one another because metacinnabar has a metallic gray color, a gray-to-black streak and a metallic-to-submetallic luster.

Other forms of cinnabar are:

  • Hepatic cinnabar or paragite is an impure brownish variety from the mines of Idrija in the Carniola region of Slovenia, in which the cinnabar is mixed with bituminous and earthy matter.
  • Hypercinnabar, crystallizes at high temperature in the hexagonal crystal system.
  • Metacinnabar is a black-colored form of mercury(II) sulfide, which crystallizes in the cubic crystal system.
  • Synthetic cinnabar is produced by treatment of mercury(II) salts with hydrogen sulfide to precipitate black, synthetic metacinnabar, which is then heated in water. This conversion is promoted by the presence of sodium sulfide.

More information about cinnabar found in: https://geology.com/minerals/cinnabar.shtml

Did you know that Cinnabar means Dragon’s blood?

Indonesia’s Volcano Spewing Blue Lava

Volcanicity and Igneous Activities

Volcanoes have inspired and frightened humans for centuries. They have been a center of folklore and myths for thousands of years. One volcano has surpassed all the other volcanoes in reputation thanks to its incredibly beautiful lava. the Kawah Ijen volcano in Indonesia’s Java island is seen as spewing bright blue lava at night. This colour is seen due to the burning of Sulphur from the volcano that burns with a bright blue flame. Kawah Ijen volcano is part of the complex volcanoes in Banywang Regency in Java.

blue lava blue-flames-of-sulfur-solfatara-kawah-ijen-volcano-caldera

 

Photo credit: Stephane Damour via Flickr.