NH Notes: Inverted Valleys – A Question of Age

Inverted valleys formed from lava “rivers” and ancient stream beds are one of many unusual geological phenomena found in Utah.  The rocks speak in Utah and they speak very clearly because they readily reveal so many clues about their origins since they are so visible to us.   Some of the most powerful testimonies of just how long and complex the geological history of the earth is don’t come from a single one of these features but result from an effort to place them into context with each other.  Context is key as I have been known to point out many times in past posts.

In my last NH Note I introduced you to flat-topped hills in the St. George Utah region (NH Notes: Ancient Lava Flows and Inverted Valleys in Utah).  I pointed out that the flat tops of these hills were in fact the remains of what had been valley bottoms that had filled with lava that flowed into them from the north long ago.  Before that I showed winding river bottoms that now form ridges further north near  Green River UT (NH Note:  The Exhumed Paleochannels of Utah and Mars) and that even Mars may have inverted valleys.   All of these inversions are a testimony to a series of historical events that have taken place over long periods of time.

For the St. George Utah region let us look at a short list of the geological features and the corresponding historical events that have taken place to produce the those features in the landscape that we see today:

1) 15,000 feet or more of layered fossil-bearing rock underlying the entire region:   St. George and the surrounding mountains sit on over 15,000 feet of fossil-bearing mostly horizontal deposited sedimentary rock.  Before there could be volcanic deposits on this rock or valleys carved into that rock those rocks had to be formed.

2)  Erosion of valleys into these rock layers:  St. George sits in a large valley eroded into what would have been thousands of feet into sedimentary rock.

3)  Volcanoes and lava-filled valleys:   At some point during the erosion of this area, volcanoes to the north spewed enough lava that it flowed 15 miles into the valleys present there at the time.   This filled the valleys with hardened basalt.  That landscape of hills and valleys would have sat hundreds of feet above where St. George is today.

4)  Erosion of the St. George area continues leaving the basalt-filled valleys as capped hills and ridges:   With the valleys full of basalt the softer sandstones of the hills erode faster and eventually streams around the edges of the basalt work they way down eroding the hills away to form valleys were the hills once stood.  The former valleys are left where they were and are now hundreds of feet or higher than the eroded landscape around them.

5)  Small volcanic eruption (Santa Clara Volcano) resulting in lava flow down into the Santa Clara river valley:  Only after this erosion of hundreds of feet of sediments occurred could the modern lava fields on the Santa Clara valley floor be formed (see images below).   A small volcano formed just north of St. George and lava flowed into the valley once again to form the lava beds that are present there today.

6) Erosion of that lava flow in canyons and partial burial of lava fields in the valley:   The lava fields on the valley floor have little vegetation but some are buried with sand.  These lava fields are thought to have several thousand to 20,000 years old in origin.

7) Occupation of the region by early Native Americans to present:  After the volcanoes went dormant people finally came to this are and Native Americans produced thousands of petroglyphs on the sandstone rocks at the edge of the Santa Clara river.   These petroglyphs are incised into desert varnish which itself takes thousands of years to form so even the boulders along the river must have been where they are today for thousands of years before the first people arrived.

How long did this take?  The original 15,000+ feet of sedimentary rock are thought to have taken 1/2 billion years to form.  Erosion of that rock continued for many millions of years to produce the valleys and hills at the time that volcanoes became active.   Conventional geological dating places the time of the large eruptions of lava from 1 to 2 million years ago.  It was during this time that the valleys were filled with lava.  The erosion of the hills around these lava flows to form the current valley were St. George sits is thought to have taken around 1 million years.  The Santa Clara volcano that gave rise to the lava fields on the floor of the current valley is thought to have been active from 5 to 20 thousand years ago. The lava fields from that volcano have clearly not eroded very much. However this volcano had likely fallen silent before any people were on the scene.  There are abundant Anasazi petroglyphs on the boulders along the Santa Clara river.  Those petroglyphs could be as old as 1000 BC up to about 1000 AD.  As I said above the petroglyphs are chiseled into desert varnish which itself takes thousands of years to form so it is very likely that the current valley where St. George sits has looked almost exactly as it does now for 10s of thousands of years.

Young earth creationists feel compelled to compress all of these events into the past 4500 years or so.  They would explain the 15,000 feet of fossil-bearing sediments as the result of a global flood but then the other historical events we have witness of would need to have occurred in post-flood times.    Why? because all these features could not have been produced simultaneously.  Geological features are the result of a series of events not a single event.   Valleys would have to be incised prior to volcanic eruptions.  The part that really is difficult to explain then becomes the erosion of hundreds of feet of sediments after these eruptions.   Young earth creationists usually want to explain vast amounts of erosion as the result of waters receding after the flood.  However, in this case they would have already used this explanation when they try to explain how there would have been valleys for the lava to fill in the first place.  How and when did the hills erode around these lava filled valleys in very short order with no significant water source? The St. George valley appears to have existed for thousands and thousands of years as it looks today, so how can all these other features be compressed between the end of a global flood and the arrival of the first people (within just hundreds of years by most YEC accounts) to this area?  Conventional geology provides a very plausible and scientifically testable set of theories for how this landscape could have evolved over long periods of time.  Young earth creationism provides nothing but ad-hoc explanations with no evidence to support them.

Below are some pictures of the most recent volcanic activity in the St. George area.  The flat-topped hills that are capped with Basalt look like very old worn basalts while these lava fields that sit hundreds of feet below them on the current valley floor look very young in comparison.

Below is a Google map picture showing the “modern” lava fields just west of St. George that lie on the current St. George valley floor. Here a golf course and homes have been built amongst the lava.

Just north of the lava fields above is this cinder cone which is presumed to be the source of the lava.  This site is much higher up and the lava would have run from here down into the valley. Notice that there isn’t a lot of worry about this volcano erupting again any time soon as homes have been built just several hundred feet from the volcano.