The Earth Story

Rafting trip on Bakota gorge downstream of Victoria Falls Zambezi river

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This is one way to use a boat I guess.

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A whopping emerald crystal

Weighing in at over 1.1 kg (5655 carats) we have this stunning discovery from the Kagem open pit mine in Zambia, glowing a deep yellowish green and relatively clean of inclusions. Found on October the 2nd, it will be auctioned in Singapore later in the year. Stones of such a huge size and quality rank amongst nature’s rarest productions and this one has been given a moniker of its own to accompany this fact. The stone is known as Inkalamu, the Lion Emerald since the mining company support Zambia’s efforts to conserve these fierce felines as part of its local beneficiation programme (and will donate 10 % of the proceeds to the charities they support, the Zambian Carnivore Program and the Niassa Carnivore Project in Mozambique).

I sincerely hope that the buyer appreciates its true value as a crystal and chooses to keep it as a unique investment piece rather than add value to it by cutting it into smaller faceted gems. The company specialises in responsibly sourced coloured stones and has nanotechnology tracing systems to allow the identification of the origin of their stones, so if it is cut the fact that individual stones came from this exceptional piece will be recorded.

Loz

Image credit: Gemfields http://bit.ly/2AEndBD http://bit.ly/2qnvtQp

Victoria Falls, Zimbabwe side

Hanging out at the edge of Victoria falls

Over the top of Victoria Falls

Devil’s Pool on the edge of Victoria Falls

Helicopter view of Victoria Falls. Awesome

Victoria Falls from far above

Astronaut Jack Fischer captured this picture while zooming in on the Zambezi River from the International Space Station. His comment, from his daughter, stated that one side was his heartbeat before having coffee in the morning and the other side was afterwards.

Anyway, this is a great geological view. Victoria Falls pours over a plateau covered by at least 300 meters (and possibly in places up to 1000 meters) of basalt, the type of lava erupted at rift zone volcanoes like those in Iceland. These basalts formed 180 million years ago during the early Jurassic as the supercontinent Gondwanaland was breaking up. As the giant continent pulled apart, rift zones were created that allowed hot mantle to flow upwards, melt and produce magma that eventually erupted at the surface.

Lava that cools down will form cracks, and these thick sheets of lava did exactly that. There are long, linear cracks running through this basalt, many of which filled with sand after they formed. That sand is now a weak, easily eroded sandstone. From this ISS photo you can actually make out several of these sandstone filled cracks – they run at different angles, but you can see how the gorges of Victoria Falls follow them.

Once the current Zambezi river integrated, it began finding weak spots in the landscape it could erode, including these sandstone layers. As seen in this shot, downstream of the modern falls are a number of steeply eroded canyons, tens to hundreds of meters deep. When the water hit one of those sandstone units, it would erode backwards in a line along that sandstone layer, creating a wide curtain of water as seen in the falls today.

The basalt is tougher than the sandstone, so the wide curtain of water pours over the basalt without stepping backwards or eroding too much. However, when the water finds another weak sandstone layer, it rapidly erodes backwards along that layer, cutting off the previous gorge and forming a new waterfall. Exactly that sort of shift is beginning to happen at tip of the falls towards the top of this frame (in this image north is roughly to the right). At an area known as the Devil’s Cataract, erosion is beginning to cut a new gorge upstream. In thousands of years, that new gorge will host the next version of Victoria Falls.

-JBB

Image credit: https://twitter.com/Astro2fish/status/895770661628465152

References: http://www.victoriafalls-guide.net/gorge.html http://www.siyabona.com/explore-victoria-falls-geology.html http://bit.ly/2vEUs3A_ _

Part of Victoria Falls

Roar of Victoria Falls, from Zimbabwe