Catastrophic Geology: Case 11

In 2014, a landslide occurred near Collbran, Colorado.  The landslide was a debris flow, a conglomeration of soil, rock, and the wooded debris, that travels similar to a liquified sand mass. Some have theorized that vibrations within the mass allow it to travel as a debris flow.  The failure was instigated by a rotational global slope instability failure near the top of the mountain, producing a headwall scarp almost 600 feet tall at its maximum height.  A cascade of subsequent landslides produced the overall catastrophic landslide that traveled approximately 2.8 miles and killed 3 men.

Heavy rain likely reduced the shear strength along some of the failure plane within fissures in the sedimentary rock mass (shale) and instigated the failure.

A study by a team from the geology department at Colorado Mesa University found that the landslide produced new deposits up to 150 feet thick maximum in a matter of minutes (not millions of years).  The new deposit includes rock boulders and buried trees and other organic debris and if subsequently buried could form conglomerate or breccia type rock or resemble a glacial till.

The geology team also observed evidence that the original topography indicated the remnants of previous landslides (ancient slump blocks evident below steeper mountain slope).

Evidence of Catastrophic Geology: Case 10

Sedimentary deposits such as alluvial terrace deposits (regional flood deposits), debris flows (landslide during flood along river or stream valley), or mud flows (saturated fine-grained soils in a landslide during a flood along a river or stream valley) can produce layers several feet thick in a single event.  At Mount Rainer for example in 2006 the Tahoma Creek was subjected to severe flooding, in some places flooding the river valley 400 feet across.  Flood flow aggredation deposited 4 feet of granular soil in a single event near the bridge at the photograph below.  The level the man is standing at was 4 feet higher than before the flood.

A park geo-scientist reported in a video presentation of the event up to 6 feet of deposition in some areas, and an accumulated 38 feet total aggredation in some areas since 1910.  That is a 38-ft thick channelized or wide valley sedimentary deposit stratum or bedded strata in less than 100 years.  Although the Tahoma Creek drainage valley is the downstream drainage feature of the local glacier, granular flood deposts can be produced along any river or stream valley where source rock is available upstream where rivers are present through rock geology.  "Aggredation" is a term used to describe the accumulation of sediment.

Use proper vocabulary

Thanks to the influence of my step-father i developed an awareness of always listening for the use of proper grammar and vocabulary, for myself in particular, since we all make occasional mistakes.  In this post i remind myself of the differences between terms used to explain the source of an opinion or condition:


Conjecture: The formation or expression of an opinion without sufficient evidence or proof.

Surmise: To think or infer without strong evidence.

Guess: To arrive at, or commit oneself to, an opinion without having sufficient evidence to support the opinion fully.

Approximate: Not perfectly accurate.

Hypothesize: To form a proposition as an explanation for the occurrence of some specified phenomena either asserted or as a provisional conjecture to guide an investigation (i.e. "he will hypothesize, although unsubstantiated, that particles-to-people evolution occurs.")

Theory: A proposed explanation whose status is still conjectural, in contrast to well-established propositions that report matters of fact.

Evidence of catastrophic geology: Case 9

"Large Igneous Provinces".  You probably have not heard of this term before.  They are defined as short duration events (i.e. catastrophes) during which large volumes of magma (lava) were produced and placed.  In 2013, a team of scientists from the University of Houston reported confirming finding the largest volcano on earth under the ocean east of Japan.  The volcano was named the "Tamu Massif" (Texas A and M University, where the lead researcher started the study 20 years prior).  The volcano is a part of the Shatsky Rise underwater mountain range and is a "shield volcano" (sides formed by magma).

The unusual shape of the lava deposit - low and broad - qualifies it as a large igneous province.  Most volcanoes that erupt under water are small with steep sides.  The broad and flat shape, however, indicates that the molten lava erupted at such an enormous rate that it traveled rapidly across the ocean floor for a long distance before it could solidify (i.e. very fast).  Lava cools due to exposure to the seawater and hardens to igneous rock.

Large igneous provinces are widespread across the planet and are evidence of a catastrophic period beyond what we can imagine.

As reported by the Univ. of Houston:

"By integrating several sources of evidence, including core samples and data collected on board the JOIDES Resolution research ship, the authors have confirmed that the mass of basalt that constitutes Tamu Massif did indeed erupt from a single source near the center."

The lava flows spread for hundreds of miles relatively rapidly, and the massif covers 120,000 square miles.

Seismic refraction data and coring data appear to indicate that some of the lava flow layers (singular events) were 75 feet thick (i.e. 75 feet of deposition in a matter of days or weeks for each event).

Evidence of Catastrophic Geology: Case 8

"Lake Tsunamis"

Tidal waves (tsunamis) do not only occur in oceans,  Catastrophic events can occur in lakes as well that cause large wave action.  Any lake within notable topography is typically at risk of experiencing a tsunami.  Lake Geneva in Switzerland has been studied impressively and geologic evidence indicates several tsunamis have occurred during the lake's existence.

As reported in Nature Geoscience, Dr. Kremer has performed notable study of the lake and theorizes that the recorded tsunami of 563 AD which devastated the city of Geneva (several historical accounts are available that describe the event) was caused by a landslide of massive rock debris into one side of the lake, destabilizing tall underwater canyons of soft deltaic sediment (where Rhone river feeds into lake).  The huge underwater global slope stability failures created the wave action that produced 0 to 14 meter tall waves (that is 46 feet max) that devastated many of the communities along the lake shores.

An image reported in the Economist magazine is presented below.

Beds (layers) of turbidite (alluvial deposits of high velocity water) in the lake help support the theory.  4 apparent beds totaling 20 feet thick may have been formed in just 4 single day events.  20 feet of wide-scale sedimentary deposit in 4 days, not millions of years.  

The layers are roughly 10km long (6 miles long) and 5km wide.  Organic material present in the first layer was carbon dated and closely matches the 563 AD age.  The sediment at the river delta also obviously accumulates very rapidly to form the dangerous underwater canyons.  Since the lake is suspected to have formed after THE ice age, the frequency of the tidal waves is a cause for concern.  When is the next one?

Evidence of Catastrophic Geology: Case 7

Rifting of tectonic plates can occur much faster than understood by many laymen.  As reported in the journal Nature in 2006, the crust on the side of the Red Sea rift moved apart by 26 feet over a period of just 3 weeks.

Magma entered the crack forming new crust.  Images from the European Space Agency's Envisat radar satellite were used (before and after) to validate the measurement.

A series of small earthquakes had occurred in east Africa the previous year, separating the rift in Ethiopia along a 37 mile long segment (East African Rift).  The Red Sea Rift can be seen in the illustration below.

(image from Saudi Arabian Geological Society)


Satellite monitoring technology has only been recently available to track movement of land masses, and many more events will be examined with keen interest.

Difference between "fracture" and "fissure"

The terms "fracture" and "fissure" are used in my geotechnical engineering reports for Central Texas geology (i.e. limestone formations typically).  These are two different terms and not synonyms.  Both are "discontinuities" in a rock mass.  Discontinuities can be categorized as:

- Fractures
- Joints
- Bedding planes
- Cleavage or foliation
- Faults

When a crack forms along a rock cleavage plane, some prefer not to associate the term fracture with this type of discontinuity.  But joints are also fractures.

A fracture develops mechanically in rock due to a failure of structure under tensile stress (the initial stage of a crack) or stress-strain conditions due to environmental or man-made conditions.  When shear stresses parallel to the plane of the crack are out of equilibrium, sliding may occur (i.e. fault).

A fissure is a specific shape of fracture, one that is long and narrow.  It is also a discontinuity dividing an otherwise continuous rock material without separation in 2 of 3 dimensions (i.e. no sliding has yet occurred; separation in 1 dimension).  A fissure may be void or may have been filled in.  A fracture or a joint with a visible opening (aperture) and a long or deep alignment can be called a fissure.