EPOW - Ecology Picture of the Week

Life on a Kopje, Part 1

Kopje Outcrop
Serengeti National Park, Tanzania

Explanation:  What is this strange rock formation, here in the otherwise flat savanna veldt country of Serengeti National Park in northern Tanzania?  

This is a kopje ... pronounced "copy."  More on this name in a minute.

Kopjes are wonderfully unique environments that contrast with the surrounding grasslands and open woodlands.  This week, let's explore some kopjes and ponder how they formed.  
  

  
When the Earth was young, some billions of years ago, molten magma extruded upwards into existing rock layers.  As it slowly cooled, it created igneous formations of gneiss and granite, still beneath the Earth's surface.
    

    
Then, half a billion years ago, in the early Paleozoic Era, the Earth's crust buckled, forcing low hills of these formations up to the surface.  In the several million years that followed, wind, rain, and other weather caused the hills to erode, exposing and leaving behind the hardest of these formations that eroded the least.  
  

  
Today, we are viewing on the tip of the kopje, like a terrestrial iceberg.  Most of these formations remain underground.  
  

  
What we see today as the flat savanna of the Serengeti plains was formed by eruptions of nine volcanoes from the nearby Ngorongoro region to the east.  Volcanic ash blew west and settled over the region, today partially hiding the kopje formations.  

According to a signboard in the park, one volcano called Oldoinyo Lengai still occasionally erupts ash into the region.
  

So how do these iconic, 
massive, rounded, 
stacked boulders form?

The smooth, rounded shapes
are a result of a process
called exfoliation,
whereby changes in
air temperature cause the
outer layers of these rocks
to expand and contract.

This eventually causes slabs
to split off, like layers of
an onion, leaving behind
these wonderful shapes.

The dark stains on the rock faces are called
desert varnish -- minerals cemented to the rock surface
by living bacteria or lichens -- which we explored
in an earlier EPOW episode.
  
  

So this is the story of the formation of kopjes.

  
And a final word here on ... words, in particular, kopje.

The word kopje -- initially koppie -- is South African Dutch, derived from kop meaning "hill"or "head."  The suffix je (or pie) was added as a diminutive, so that kopje means "small hill."  

And, in turn, the word kop is Afrikaans, from the Dutch meaning "head."

Now you know.

Next week we will further explore life on a kopje -- what could possibly live in this seemingly barren and inhospitable environment?