Presentation on theme: "Catastrophism. Uniformitarianism The assumption that the natural processes operating in the past are the same as those that can be observed operating."— Presentation transcript:
Uniformitarianism The assumption that the natural processes operating in the past are the same as those that can be observed operating in the present. Its methodological significance is frequently summarized in the statement: "The present is the key to the past." the observation that fundamentally the same geological processes that operate today also operated in the distant past. quoted from Wikipedia.com
Catastrophism Is the theory that Earth has been affected by sudden, short-lived, violent events that were sometimes worldwide in scope. Catastrophism can function with or without assumptions of long timelines. Geologists combine catastrophist and uniformitarianist Catastrophism explains certain events that Uniformitarianism cannot quoted from Wikipedia.com
Various Earth Craters Serpent Mound Crater, Ohio 320 million years old
Various Earth Craters Barringer Meteor Crater, Arizona 49,000 years old
Manicouagan Crater 214 million years old
Chicxulub Yucatan, Mexico 65 million years old
Parts of a Crater
Types of Craters Simple Complex
How Meteors Effect Statrigraphy and are useful to Geologists Interruption of normal rock sequences Can create thick local beds that are unique to that particular isolated event Can create thin beds that can cover the globe Effective for Age dating adjacent rock layers Mark mass extinction boundaries Can change global earth conditions in both atmospheric properties and biospheric Make for money for Hollywood =)
Upheaval Dome, Utah <170 Million years ?
Features 500 m-deep, The inner most ring is 1500 m-wide The outer most ring is over a 3 km wide Central depression of soft, deformed rocks eroded away by a tributary of the Green River Extremely deformed Moenkopi Formation Center of crater has up to 500 m of displacement Apparent complex crater shape
Salt Dome or Crater?
Dome theory A salt dome forms when a thick layer of evaporate material is buried under many subsequent layers of rock. The weight of these rock layers put pressure on the salt layer and over time the salt will find a fault to travel along. The salt then moves upward and deforms the surrounding rock layers forming a dome like structure.
The Paradox Basin During the Pennsylvanian Period most of Utah was covered by ocean This was due to the prior formation of a NW fracture system that ran some 200 miles This caused a subsidence in the Earth’s crust and ultimately altered the Moab area at this time It was a huge sink hole This basin would fill with sea water and evaporate. This process would repeat over and over until there was a thick layer of salt deposited Today the layer of salt is up to1000 ft thick in places We now call this the Paradox Basin Since then there have been many more layer placed above this formation. These layer have put a great deal of pressure on the salt and salt under pressure is unstable. Over millions of years the salt has flowed and warped the above layers of rock. This creates many distinct surface features. Salt Anticlines are present here today Salt plays a very important role in current day Paradox Formations
Since Upheaval dome is in the vicinity of the Paradox formation there has been speculation that it is result of Diaper. Diaper is the idea that non-igneous, relatively cold materials under pressure will become buyout and ascend through more dense heavy material. This is the original theory of the formation of Upheaval dome. This seams to be the most simple explanation
Impact Theory A meteor smashed into the park This warped the immediate and surrounding bedrock forming a crater Over time the upper layers of bed rock weathered down to what we can see today exposing the lower portion of the impact site
Typical Impact Crater Characteristics Presence of shatter cones that are in situ Presence of multiple planar deformation features Presence of high pressure mineral polymorphs within in situ lithologies Morphometry. On other planetary bodies, such as the Moon and Mars, we rely on the shape of the impact structure to determine its presence and type (simple versus complex, etc.). This is a megascopic quality Presence of an impact melt sheet and/or dikes, and impact melt breccias that were generated due to hypervelocity impact Pseudotachylyte and Breccias: Pseudotachylyte is a rock type generated by faulting at either microscopic or macroscopic scales. quoted from ImpactDatabase
Evidence Wingate exposed on the north edge of the central depression Napkin-ring'' folds Evidence of radially-inward compression
Uplifted Kayenta and Navajo sand stone
Fractured and faulted Kayenta sandstone
Shatter cones and Shocked Quartz In 1993 Two scientists, Eugene Shoemaker and Ken Herkenhoff, discovered shatter cones within the sandstone of the crater Scientists think that shatter cones are rocks that form lineated structures from high velocity impacts Shatter cones have been found in other impact craters and at nuclear test sites Shoemaker and Herkenhoff also found shocked quartz Shocked quartz is quartz that has been greatly fractured by high energy impacts
The last piece Seismic Refraction In 1995 John Louie, a seismologist at the University of Nevada-Reno put together a team of seismologists to see if the was in fact a salt dome underneath the crater floor… here is what they found
Conclusion Upheaval dome is probably an impact crater Fractured and deformed bedrock is consistent with an impact scenario Samples of shocked quartz and shatter cones Seismology does not reveal a underling salt dome intrusion