Between a Rock and a Hard Place

Science Snap (#28): Brandberg Massif, Namibia

Elspeth Robertson June 26, 2014

The 120 million year old Brandberg Massif, Namibia. Image credit: NASA

Brandberg Massif is Namibia’s highest mountain, but if you look from above, you’ll notice it’s no ordinary one. Brandberg is a single mass of granite that pierced its way through the Earth’s crust into the Namib Desert. Looking at the Landsat 7 image, Brandberg is a circular dark and steep-sided mountain, imposing itself over the desert below. It reaches height of 2.5 km and stretches across 31 km.

Nowadays, the landscape is geologically quiet but the Brandberg intrusion formed over 120 million years ago and marks a period in the Earth’s history where volcanism was rife due to the break up of the supercontinent Gondwana. The majority of the Massif is composed of homogeneous medium grained biotite-hornblende granite. However, to the west there is a 2 km diameter pyroxene-bearing monzonite and in the south it is crosscut with arfvedsonite granite dykes and sills. As the Massif protrudes from the landscape, it influences local climate by drawing in the rains. The rain then percolates through the granites and washes out through springs.

Apparently, if you reach the granite for sunrise or sunset, you’ll see it glow red under the suns rays. Appropriately, the locals call it Daures, “the burning mountain”.

Science Snap (#26): Angel Falls, Venezuela

Charly Stamper May 1, 2014

Sorcha McMahon is a third year PhD student in the School of Earth Sciences at the University of Bristol. Sorcha is investigating how strange igneous rocks called carbonatites may have formed, using both natural samples and high-pressure experiments.

Canaima National Park. Photo credit: Sorcha McMahon

Angel Falls is the world’s highest uninterrupted waterfall in the Canaima National Park, a UNESCO World Heritage site in the Gran Sabana region of Bolívar State, in Venezuela. The waterfall drops from the summit of the largest tepui (table-top mountain) of the Guiana Highlands of South America, Auyantepui, from a height of 979 m.

Angel Falls is said to have inspired the setting of the Disney animated film Up (2009) where the location is called Paradise Falls. The nearby Mount Roraima inspired the Scottish author Arthur Conan Doyle to write his novel The Lost World about the discovery of a living prehistoric world full of dinosaurs and primeval plants. The borders of Venezuela, Brazil, and Guyana meet on the top of this tepui, which translates to “house of the gods” in the native tongue of the Pemon, the indigenous people who inhabit the Gran Sabana. Tepuis host a unique array of endemic plant and animal species, with ~1/3 of the plants found nowhere else on the planet.

Angel Falls, Venezuela. It is also known as “Kerepakupai Vená” in the original indigenous Pemon language, meaning “waterfall of the deepest place”. Photo credit: Sorcha McMahon

The extraordinary topography is part of the Guiana Shield, and began as the Great Plains; an igneous-metamorphic basement formed during the Precambrian as part of the supercontinent Gondwanaland (approx. 3.6 – 1.2 Ga). Subsequently, sedimentary layers were deposited between ~1.6 – 1 billion years ago; the characteristic purple quartzite and sandstone strata probably represent shallow seas or large inland lake facies. Doleritic and granitic magmas of Palaeozoic and Mesozoic times are observed to penetrate existing sediments in places.

The region has experienced great fluctuations in climate and several periods of uplift and subsidence over millions of years. The presence of isolated table-top mountains is due to relative differences in erosion, which has created such spectacular scenery.

Science Snap (#25): Vesuvius, Andy Warhol

Elspeth Robertson April 21, 2014

Vesuvius by Andy Warhol. 1985. Credit: Gaetano Anzisi

Quite simply, volcanoes are inspiring. I’ve yet to meet someone who disagrees. The majestic volcanic landscape has thus been an inspiration to many an artist and author, whether intentional or not. Furthermore, artwork itself can be a valuable tool to help decipher and understand eruptions and their effects on the climate.

Pictured here is Vesuvius erupting in all its glory and is one of my favourite pieces of “volcanic arc”. Andy Warhol made a few variations on this theme so have a google, take a look around and enjoy (there are not many pictures available on creative commons though so can’t be included here!)

Science Snap (#24): The psychedelic Zambezi flood plain

Elspeth Robertson April 19, 2014

Zambezi River, Zambia. credit: ESA

This colourful image shows the Zambezi River’s floodplain in Zambia. The image was created from three acquisitions from Envisat’s radar instrument that were merged together. Each acquisition was assigned a colour and when combined show changes in the floodplain between each satellite acquisition.

The white patch of pixels in the upper right quadrant marks the city of Mongu and appears white as few changes occur between each satellite image. In light green and running up the center of the image you can track the main channel of the Zambezi river. However, one image was taken during the wet season when the water levels rise up to the edge of the town. The range of colours in the image attest to the dramatic changes in water level of the Zambezi between wet and dry seasons.

Original ESA article can be found here.