Tabula Rasa

This blog is supposed to be about rocks. This time, it is!

The literal translation of Tabula Rasa from Latin is “clean slate”.

In more general terms, it’s “the idea of individuals being born empty of any built-in mental content, so that all knowledge comes from later perceptions or sensory experiences.” (Wikipedia) Recent advances in our understanding of genetics and pre-natal development cast some doubt on the concept of Tabula Rasa.

But Roxy and I just like the way it sounds. So, we used it to name our favorite rock on Happy Hillside next to KinesavaROCKS Universal Headquarters. They’re on our property - so we get to call them anything we want. We name everything.

This rock …

… is named “Ice Cream Sundae”.

The rock just below it is “Chuckalot” (like “Camelot”) because a Chuckwalla makes his home in the deep crack.

This dead tree …

… is named “Wraith”.

The doves just love to roost on Wraith.

Tabula Rasa is our favorite. Roxy said I should tell you that Tabula Rasa is over 20 feet tall … top to bottom.

The waves you see in the surface of Tabula Rasa are called, “ripple marks” They were formed in fine silt and sand about 200 million years ago and frozen into stone by compression and deep time (See my blog, Deep Time.) to create the Navajo Sandstone formation. I count 10 bands of ripple marks across Tabula Rasa. Bands of truncated ripple marks like this are referred to as “cross bedding”. These bands of ripple marks are caused by a change in whatever created the ripples marks in the first place, which can be either wind or water.

That’s the simple explanation. From there, it gets complex. Whether these ripple marks were an ancient seashore or a massive sand dune was in dispute for a long time. The prevailing opinion of geologists today is that the 1500 foot thick Navajo Sandstone was once a vast desert of sand dunes. But the pioneer geologist Clarence Dutton – he worked for John Wesley Powell and Lake Powell was named for him – concluded that they were deposited by an ancient sea.

You can still see scholarly debates between geologists about the fine details of the formation of the Navajo Sandstone. Based on what I have heard from professional geologists about my dad's rocks, color me surprised! .... (/sarc/)