One dune, on its own, moving
The Shifting Sands is a solitary crescent dune of black volcanic ash sitting on the open plain in the western part of the Ngorongoro Conservation Area, north-west of Olduvai Gorge. The Ngorongoro Conservation Area Authority places it at least twelve kilometres from the Olduvai museum and nearly two kilometres from the gorge’s bank, and elsewhere gives the distance from the museum as ten kilometres.
What makes it unusual is not its size. It is that a barchan dune of this kind normally occurs within a much larger dune field, and this one stands entirely alone in short grassland, black against a pale plain.
Where the NCAA’s own figures disagree with each other
The authority’s page for the dune carries a block of prose and a row of statistics, and they do not match. Taking them side by side:
- Rate of movement. The prose gives approximately 15 to 29 metres a year. The statistic tile gives 17 metres a year.
- Height. The prose says it reaches exactly five metres. The statistic tile says nine metres.
- Length. Both give 100 metres along the curve, which the prose also renders as 328 feet. This is the only value the two agree on.
No source reconciles them, so none of the disputed values is presented here as the answer. The dune is roughly a hundred metres across its curve, somewhere between five and nine metres high, and moves west across the plain by something in the order of twenty metres a year.
What it is made of, and why it holds together
The ash is natrocarbonatite material from Ol Doinyo Lengai, the active volcano to the north-east. The NCAA describes the dune as highly magnetic, which is what binds the grains together and stops the wind simply dispersing them, and it attributes the dark colour to iron-rich minerals: the wind has scoured the lighter fraction of the ash away from the surrounding ground, leaving the heavy dark material to build the dune.
The dunes are well exposed above the plains and, in the NCAA’s description, easily accessible by trails running down from the Olduvai Gorge ravine towards the eastern grasslands of the Serengeti on the conservation area’s side. The authority confirms plainly that the site can be reached by vehicle, and says the Olduvai Gorge Museum curators are the people who explain it.
What a visit is like
It is a short stop and an odd one. There is nothing built here. The dune is a black crescent a few metres high that you walk up to, walk around and look at, and the interest is almost entirely in knowing what it is and where it came from — a pile of ash from a volcano eighty kilometres away, crawling across a plain and leaving no trace behind it.
Anyone expecting a desert landscape will be disappointed within a minute of arriving. Anyone who has just come from the Olduvai museum and understood the geology will find it one of the more memorable twenty minutes of the trip. That is a real difference, and it is the argument for doing the two in that order.
Common questions
How fast does the dune move?
The NCAA’s own page gives two different answers: approximately 15 to 29 metres a year in its text and 17 metres a year in its statistics. Both are published by the same authority on the same page.
How high is it?
The NCAA’s text says exactly five metres; its statistics say nine. The length along the curve, 100 metres, is the one figure the two agree on.
Can you drive to it?
Yes. The NCAA states directly that the shifting sand area can be reached by vehicle, and describes the site as easily accessible by trails from the Olduvai gorge.
Where does the ash come from?
From Ol Doinyo Lengai, the active volcano north-east of the conservation area. The grains are magnetic, which is why they hold together instead of blowing away.