The Palisades basalt sill is one of the most active mass movement areas in New Jersey (Pallis, 2009) and because of its activity it is important to understand the underlying mechanisms that cause the rockfalls along the outcrop. The Palisades are composed ancient Jurassic flood basalt that formed through at least three distinct intrusion events (Puffer, 2009). It is important to understand that in all of these events the molten magma was allowed to completely cool before the next event allowing for the formation of the iconic hexagonal columns of basalt (Puffer, 2009). These columns are referred to columnar joints and formed when the molten basalt cooled within the earth's crust. The cooling of the basalt caused it to shrink, creating vertical fractures along the weakest planes of the newly formed rock (Puffer, 2009). These joints are called primary joints due to these columnar joints forming as the rock itself formed (Linsey, 2014).
Studying the effects of weathering and erosion on the uplifted and exposed basalt sill is important to understanding the geological events that lead to mass movements in the area. My researc sought to determine exactly what happens to a rock that has been exposed to natural weathering such as thermal, biological, chemical, and wet-dry also referred to as slaking, on a qualitative and quantitative scale. The weathering of the rocks, though apparent on the exterior of the sample, has an extreme and transformative effect on the internal structure (Gupta et al., 1999). Weathering disrupted the internal crystalline structure by producing microfactures, voids, and the deposition of clay minerals (Gupta et al., 1999). Basalt is heavily affected by weathering when concerning porosity and the formation of ...
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...2006) observations: Geomorphology, v. 99, p. 353-368.
Matsuoka, N., and Sakai, H., 1998, Rockfall activity from an alpine cliff during thawing periods: Geomorphology, v. 28, p. 309-328.
Monthly Average Temperature for New York, NY: http://www.weather.com/weather/wxclimatology/monthly/graph/USNY0996 (March 2014).
Pallis, Ted, 2009, New Jersey Landslides: New Jersey Geological, Information Circular, p. 1-4.
Puffer, J., Block, K., Steiner C., 2009, Transmission of Flood Basalts through a Shallow Crustal Sill and the Correlation of Sill Layers with Extrusive Flows: The Palisades Intrusive System and the Basalts of the Newark Basic, New Jersey, U.S.A.: Journal of Geology, p. 139-155.
Yan, F., Feng, X., Chen, R., Xia K., Jin, C., Dynamic Tensile Failure of the Rock Interface Between Tuff and Basalt: Rock Mechanics and Rock Engineering, May 2012, v. 45, p.
The shelf-edge includes carbonate-to-clastic facies transition and tectonic uplift and erosion of the carbonates followed by deposition of the clastics. The Saint Peter Sandstone is a well-sorted, almost pure quartz arenite deposited during a major mid-Ordovician low stand. Clastics spread across an exposed carbonate platform by transportation. This is shown by the well-rounded, frosted texture of the quartz grains.
The third alluvial deposition consists of sand, silt and minor inter-bedded gravel, and again indicates Brimbank Park’s changing geology over time. (Geological map of Victoria, 1973). These deposits, as well as a nearby fault suggest volcanic activity 5-1.6 million years ago, which explains the olivine basalt (fig. 2) deposits which date back to to the Silurian and Tertiary period.
...e morphed it into the quartzite that is seen surrounding the butte (4). Rocks that undergo this process are called metamorphic rock, which is the same as the rock seen years ago by dinosaurs and other extinct creatures. The quartzite rocks were formerly seafloor sediment that was forced upwards, and then surrounded by lava basalt flows. Once erupted through fissures and floods through out most of the area, lava flow eventually created enough basalt to form a thickness of about 1.8 kilometers (1). All of this basalt flow eventually led to the covering of most mountains, leaving the buttes uncovered. The igneous lava flows and loess is reasons that the Palouse consists of such sprawling hills, and rich soil for farming (2). In result of the lava flows, the Precambrian rock Quartzite was formed. And lastly covered by the glacial loess, which were carried by the wind.
The Franciscan Terrane of central California represents an accretionary complex formed by long-term subduction of an oceanic plate under the Western margin of the North American craton. The Franciscan complex is composed of three distinguishable belts: the eastern belt (Yolla Bolly and Pickett Peak terranes), the central belt, and the coastal belt. Age and metamorphic grade of the belts decreases to the west (Blake and Jones, 1981). Formation of the accretionary complex began during the late Jurassic in the eastern belt and has continued into the Miocene along the western coastal belt. The complex trends NNW and is bounded by the San Andreas Fault to the east and by the coastal range fault to the west. The coast range fault separates the Franciscan complex with the partly coeval Great Valley sequence. Debate exists over the tectonic evolution of the Franciscan, centered around the geographic origin of the Franciscan rock units.
At the end of the last ice age windblown silt covered the lava and basalt deposits. This silt would go on to create the fertile rolling hills of the Palouse. This soil is more than a hundred feet deep in places. Soon, enough time passed for vegetation to take place and more soil started to form.1 The lava flows would end up damming streams flowing from the mountains; in turn forming the current lakes of the region. Layered between the flows of basalt are sand and gravel deposits that washed down from mountains.1
Plummer, C.C., McGeary, D., and Carlson, D.H., 2003, Physical geology (10th Ed.): McGraw-Hill, Boston, 580 p.
Basalt is a commonly occurring igneous rock. More specifically however, Basalt falls under the category of Mafic Rocks. Mafic rocks have a poor Silica content, approximately 50% (Charles, Diane, Lisa, 2010) and contain high concentrations of metal oxides. Basalt is a fine grained rock containing predominantly ferromagnesian minerals, followed by plagioclase feldspar. The colour of Basalt ranges from dark grey to black and is relatively featureless. See Fig 1.
In this report, I will be discussing the formations of tuff rings, tuff cones, and a variety of spectacular geologic features that can be seen in the Southern Oregon area (near Silver Lake); including Hole in the ground, Fort-Rock, and Table-Rock complexes. To begin, we will start with the background of how tuff rings and tuff cones are formed. Hydrovolcanic eruptions are some of the most violent spectacles, each generating hundreds, or even thousands, of explosions throughout the course of its eruption. Each eruption ejects a mixture of clasts, gas, and water droplets which either fall to the ground or evaporate into the atmosphere. These deposits build up rings of bedded tuff around the volcano’s vent, which in the long run, helps geologists to record the varieties of pyroclastic depositional mechanisms and important changes that occur to the feature with time. The basaltic deposits from the Hydrovolcanic eruptions which occurred in the Fort Rock-Christmas Valley Basin was also formerly the location of an intermittent, fluctuating, and wide-spread Pleistocene lake (fossil lake). Primarily basaltic volcanoes erupted in the center of what was once a lake basin, forming the maar-style volcanism that is prevalent in Southern Oregon, today.
Tarbuck E., Lutgens F., Tasa D., 2014, An Introduction to Physical Geology, 5th Ed, Pearson Education, Upper Saddle River, New Jersey.
Stone Mountain rises in sharp contrast to the surrounding flat, rolling landscape creating a geomorphic monadnock. Geologists appear to have consensus of the volcanic origins and underground formation of t...
All naturally occurring stone arches are formed by the selective erosion of rock, but the terms by which this can occur are massive. Among the most frequent types of formation are wave action and lava flow. During wave action, water crashes constantly upon the rock, effectively accelerating erosion while sediment carried by the water is extremely abrasive, removing bits of rock. When lava flow occurs, the outermost la...
Chemical Weathering is when water weakens the structure of the rock and Mechanical Weathering is where water seeps into the rock face causing fragments of rock to break off.
In the west, the Dakota sandstones are reminiscent of the transgression and regression of the Epicontinental Sea. Tectonic deformations and erosion continued as we see in folded and faulted rocks in the Rocky Mountains. Bentonite, present in that part of North America, proves the active volcanism of the time.
inferred for the reservoir (4). The magma ascent to the surface occurred through a conduit of possibly 70 to 100 m in diameter (5). A thermal model predicts that such a reservoir should contain a core of partially molten magma (6) that can be detected by high-resolution seismic tomography.
The interior structure of the earth is made up of crust, the mantle and core (inner core and outer core). Earthquakes occur on the crust. Crust forms the external layer of the earth surface. On the crust, the plate tectonics forces are in charge of causing the abrupt earth movements. Due to the existence of an immense temperature and concurrent pressure difference in the outer layer and inner layer of the earth, convection currents occur at the mantle. This energy results from overwhelming decomposition of radioactive substances contained by the rocks found at the interior of the earth. The developed convection currents lead to movement of lava; cold lava finds its way to the interior of the earth crust, while the molten lava which is generally hot, leaves the interior of the earth to the outside of the earth crust. These kinds of circulations occur at different locations of the earth surface and consequently results in segmentation of the earth due to movement in different directions.