planning my escape

You’ve probably seen the Redwall Limestone before

The Redwall Limestone might very well be the single most distinctive unit in Grand Canyon. Passengers flying overhead in airplanes can often make out its massive, red-stained faces.

The Redwall is a limestone from the Mississippian period. At this time, a great, warm, tropical seaway covered the Western portion of North America. All sorts of life lived in these seaways, forming all sorts of shells and leaving enormous piles of fossils and carbonates that wound up as hundreds of meters of limestone.

Dogs aren’t colourblind. They do in fact see colour, just differently to humans.  We know this because of something called photoreceptors. 

They are specialised cells in the retina of the eye. There are three known types; cones, rods and ganglion. Rods contain only a light-sensitive pigment and therefore can only detect light to dark, movement and shape. The cones are responsible for colour vision, and the number of types of cones a species has dictates the colour they can see.

Humans have trichromatic vision meaning we have three primary types of cones, or primary colours; red, green and blue. So we can see colours based on a combination of these three primary colours.

Dogs however are dichromatic; meaning they only have two primary colour receptors; blue and yellow. This means they cannot distinguish between green,yellow or red objects.

Knowing dogs primary colour receptors we can combined all combinations of blue and yellow and determined all the colours dogs can see and therefore get a pretty good idea of how dogs see the world compared to us.