Geological History and Hazards in San Diego

The new volcanic material welling up into the void, which forms a ribbon of new materials and breaks down its center gradually, when the plates move apart from the axis of the mid-oceanic ridge system. Therefore, every separating plate accretes one half a ribbon of new lithosphere, and, thus, a new surface is added (Pitman, W.C, 2007). The process is continuous, and separation is always happening at the

The Ouachita Mountains were also created with the collision of Gondwana as it pushed together seafloor and are tilted or twisted folds of earth crust. Streams usually flow along the folds. Most of the mountains are made up of sandstone and shale from the bottom of the former sea. This region is usually known for unique quartz crystals,

The three faults being considered are thought to have influenced the character of some 120,000 square miles. The Big Pine, Garlock, and San Andreas faults are all mutually active, deep, long, and steep and noted as being conjugate shears. In concert, the faults have defined a primary strain pattern of relative east-west extension and north-south shortening of the area of 120,000 square miles. The large region is noted for its deformity, with the source of this being a northeast-southwest counterclockwise compressive couple. The compressive couple was potentially supported through drag as a result of the deep-seated movement of rock material from the Pacific region (Hill & Dibblee, 1953). The interaction of the faults in the San Andreas region since the Jurassic period have served to shape and contour the present geology of the land, while a study of the paleontology of the region likewise requires such knowledge to effectively determine conditions at any given point in time.

The city has a mild year-round climate with an average of 201 days above 70 degrees. A sign of global warming is that the average surface temperature of the water has increased 3 degrees since 1950. San Diego lies on approximately 200 deep canyons and hills, creating small pockets of natural open space scattered throughout the city and giving it a mountainous geography. Due to this scattered open space, it causes a significant change in climate over short geographical distances. The San Diego River runs through the middle of San Diego while several reservoirs lie between and also separate the developed areas. The city also runs through two fault zones, the Rose Canyon and Point Loma faults, which are part of the San Andreas Fault system. It

For example, The appalachian Mountains were formed by a massive continental collision over 300 million years ago. According to page 88 in my science notebook, the rocks in the Chattooga River is evidence of the continental collision. Mountains are formed when two continental plates collide, and form the mountains. The Appalachian mountains, were formed during Pangea. The North American Plate and the African Plate collided. When this happened the Appalachian Mountains were formed. These mountains then grew bigger, but as soon as it started growing, it also eroded. Erosion and

To support the theory of continental drift is through topography, surveying the floors of oceans, charts of rock magnetism, and statistics on rock ages (Trefil & Hazen, 2010). At one time scientist believed that the deep ocean floors were flat; accumulating the sediment that progressively wore away from the prehistoric landmasses (Trefil & Hazen, 2010). However, they discovered steep-walled valleys and elevated highlands. This was evidences that just as the continents are transformed and are active, so to is the seafloor (Trefil & Hazen, 2010). The Mid- Atlantic Ridge, positioned in the central part of the Atlantic Ocean, is recorded to be the longest mountain range on this planet. Volcanoes, lava flow, and earthquakes are a source of

The creation of the Ring of Fire is very interesting too, it is the result of plate tectonics. These are huge slabs of Earth’s crust that fit together like the pieces of a puzzle. These plates can collide, stay apart, or move up right next to each other. The convergent plate boundaries are formed by plates colliding into each other. The heavier plates slide under the lighter plates causing a deep trench in the ocean floor, as we talked about earlier. If you went down into the ocean you’d be able to see a bunch of trenches in the ocean floor running parallel to corresponding volcanic arcs like the Ring of Fire. This allows islands and continental mountain ranges to be created. A divergent boundary is formed by

The Mesozoic tectonic history of the North American Cordilleran region is very complex and involves:

First, we must examine the sedimentary formations; when they were formed, how they were formed, and what materials they consist of. About ninety-three to one hundred million years ago, the Western Interior Seaway rolled through the North American continent, eventually reaching the geographical area of today’s Mesa Verde National Park (National Park Service 2005). This sea deposited a thick, hard sandstone base that is called Dakota Sandstone, although this layer is not exposed in the park

The land rose up and created a precipitous eastern edge of the batholith and a gentle western edge. 10 million years ago, uplift, which is the vertical rise of Earth’s surface due to natural causes, started to occur and accelerated quickly. Soon, the Sierra Nevada Mountain Range that we know today towered 14,000 feet in elevation. Throughout uplift, cracks formed in the granite of the mountains. They formed due to the pressure that came with the uplift. The erosion that stripped away most of the overlying rocks caused the remaining rock to expand and crack. These cracks are still forming today and they provide a template for future erosion.

Convection currents may bring magma to the surface at diverging boundaries. Sedimentary rocks from the ocean floor gets pushed down to the mantle at convergent boundaries. The crust soon melts and rises to the surface creating igneous rock. Typically mountain ranges are metamorphic rock, maybe our mountains are.

Previously, the geology of Death Valley National Park and Yosemite National Park in the Basin and Range Province and Sierra Nevada Range respectfully were discussed. West of Death Valley, is the Sequoia and Kings Canyon National Parks in the Sierra Nevada Range in California. The Sequoia National Park is also 629 square miles and includes 403,482 acres while Kings Canyon is 722 square miles with 461,901 acres(739). Interestingly enough, in Spanish Sierra Nevada means “snow-covered mountain” although many people think that it doesn’t snow in California. Since the Yosemite National Park, Sequoia, and Kings National Park are a part of the Sierra Nevada Range, there will be similarities and differences in their geology.

In the eastern part of the plateau most of the carbonate strata is Fredericksburg and Washita rock (Barker and Ardis 1996, 5). The plateau is dominated by a flat undistinguished plain, with the exception of the caprock mesas, the broad alluvial fans and the Balcones fault zone (Barker and Ardis 1996, 5). During the Paleozoic era the Ouachita Orogeny tectonic event occurred depositing marine sea deposits of upper Permian sediments and evaporates into the Permian basin, which is above parts of the Edwards-Trinity plateau aquifer (Anaya 2001, 107). Another prominent structural feature is the Llano uplift which is comprised of Precambrian rock mostly granite, located in the northern Hill Country area (Anaya 2001, 107). The Balcones fault zone was created from tensional stress from the uplift and deposition of sediments into the Gulf of Mexico, along the Ouachita belt, forming the faults by displacing the sediment 900 to 1200 feet (Anaya 2001, 109). The Edwards-Trinity plateau has two regional confining layers, Navarro-Del Rio, which confines the Edwards aquifer, and the Hammett that confines the Trinity and the Edward-Trinity aquifers (Barker and Ardis 1996, 2). The Navarro-Del Rio confining unit is regionally continuous within the Balcones Fault Zone; it is comprised of Buda limestone, Navarro Group,

All of the volcanic and metasedimentary rocks are metamorphosed, whose grades are extending from greenschist to upper amphibolite, characterized by low-pressure but high-temperature (Isachsen & Bowring, 1994). The influence of basement fracture zone is reflected in the homoclinal and abruptly alternated trends of the volcanic belts, which is more frequently found in the southwestern domain of the province, while north belts show angular patterns (Fyson & Helmstaedt, 1988; Padgham,1992; Padgham & Fyson, 1992). Except for the sharp dips of the volcanics, regional-scale folds, foliations and cleavages over several successions shown in the metasedimentary rocks are studied to understand the deformation and metamorphism (Isachsen & Bowring, 1994). Fyson & Helmstaedt (1988) compare three major types of folds which are ranked by their ages and sizes from oldest, most extensive F0 to minor-sized, cleavage-foliation-associated S3 folds with intermediate type F1 between them and they suggest that the parallel trend and they suggest both foliation and folds are results of syntectonic

* Measurements of Geologic uplift and slip rates – in many areas of the San Andreas Fault a detailed record of strike-slip activity is provided. By studying the sediments deposited in a given area and comparing them to an established age control it is possible to determine the rates and timing of changes of tectonic deformation.