Black River - River Capture Earthcache EarthCache

The Gaspereau River has intercepted the Black River at White Rock, Kings County, leaving an underfit stream to occupy the lower portion of the valley known as Deep Hollow. This is an example of River Capture.  

Stream capture, river capture, river piracy or stream piracy is a geomorphological phenomenon occurring when a stream or river drainage system or watershed is diverted from its own bed, and flows instead down the bed of a neighbouring stream.

Geology

Dendritic drainage patterns develop on unconsolidated sediments with an even slope and on evenly resistant rocks with moderate to high relief  This is exhibited by the soft Triassic sediments in the Annapolis Valley , around the Minas Basin. The drainage patterns across Nova Scotia have developed almost entirely since the Tertiary the (Tertiary Period, the former term for the geologic period from 65 million to 2.58 million years ago)  and are closely tied to the geology.  They are the response of water flowing down an inclined plane to the structure and composition of the underlying rocks. Water follows lines of weakness, such as soft strata, joints or faults, and establishes a characteristic drainage pattern. The water flow used to flow from North to South sending the Black River towards the Cornwallis River through the Deep Hollow. After the ice age and glaciers melted and moved along to create the valley floor the river was then diverted to run into the Gaspereau River.

In Nova Scotia, drainage patterns diverge from their ideal form because of three influences: the Pleistocene glaciation, which scoured the surface of the province and then dumped unsorted rock debris upon it. Fluctuations in sea level; and ancient river channels, which developed before the Tertiary drainage and are now superimposed upon the terrain.

ROCK TYPE

Potential for erosion, permeability and jointing of the bedrock determine both the proportion of water that is retained on the surface and how runoff is channelled. Impermeable, poorly jointed rocks ,such as granite, greywacke and slate, retain most of the water on the surface in a disorganized series of streams, lakes and bogs. This is called deranged drainage and can be seen on the South Mountain and across most of southern Nova Scotia. The Black River formerly drained through Deep Hollow into the Cornwallis River and is an example of river capture . The more vigorous Gaspereau River has diverted the Black River at White Rock. Black River, is a deranged drainage pattern, now extensively dammed for hydroelectric power.

Below is a map of the flow for Black River before and after River Capture. The green is the upper river flow, the red the before river capture flow and the blue is the after river capture flow.

To log this Earthcache visit the viewing location.  Please answer the following questions and send in a timely manner to my geocaching profile or email. Answers not received will result in deleted logs.

1 - How high is the wall of the gorge that diverted the river?

2 - What formed the gorge and when did it happen?

3 - Do you think the Gaspereau River was as dominate before Black River was diverted into it?

4 - What is elevation at the viewing point?

5 - Post a picture of the gorge with the background.

[REQUIRED] In accordance with the updated guidelines from Geocaching Headquarters published in June 2019, photos are now an acceptable logging requirement and WILL BE REQUIRED TO LOG THIS CACHE. Please provide a photo of yourself or a personal item in the picture to prove you visited the site.