Welcome to GEO 101 Introduction to Geology
so what is Geology?
not just rocks!
Geology is... study of Earth and planetary bodies processes responsible for formation processes that modify
all areas of geology have either economic or environmental importance: earth resources topography (study of landforms and processes responsible for their formation) natural hazards (floods, volcanism, earthquakes) waste disposal and pollution cleanup climate change
Geology is a physical science with many sub-areas of study or sub-disciplines: mineralogy - petrology - geochemistry - volcanology stratigraphy - sedimentology - paleontology geomorphology - surficial geology - hydrogeology structural geology - tectonics - geochronology solid-earth geophysics - rock mechanics
Geology is also an applied science that interfaces with engineering and deals with: environmental and groundwater use (environmental geology) oil and gas exploration and exploitation (petroleum geology) metal and non-metal mineral exploration and exploitation (economic geology)
... so what is the modern context in which we will be examining Earth?
The Dynamic Earth a system of various subsystems or related parts (atmosphere, hydrosphere, biosphere, and solid earth) interacting in organized fashion
initially homogeneous, but with cooling separated into distinct concentric layers: Layers Crust Mantle upper lower Outer core Inner core brittle lithosphere ductile asthenosphere
Layer Thickness Nature Inner core 1216 km solid iron-nickel alloy Outer core 2270 km liquid iron-nickel alloy Mantle ~2885 km solid (Mg-rich silicates) upper (shallow) - intermediate density lower (deep) - high density Crust 65 km solid (low to intermediate density silicates) Oceanic Crust (5-10 km) - high density (Fe-Mg rich) Continental Crust (30-65 km) - low density (Fe-Mg poor)
solid Earth composed of rocks divided into three groups based on mode of formation: igneous - formed by cooling and solidification of molten rock (magma) sedimentary - formed by precipitation from solution, compaction of plant and animal remains, or cementation of particles from pre-existing rocks metamorphic - formed below surface under high temperatures and pressures from pre-existing rocks
different rock types related to each other by: rock cycle
Geologists interrelate Earth processes, rock types and physical features through global pattern of change described by what has become known as Plate Tectonic Theory
Earth's brittle outer shell or lithosphere (crust and uppermost mantle) broken into coherent pieces or plates that move slowly over the ductile asthenosphere
three major plate boundary types marked by earthquakes, volcanism, or both
divergent plate boundary plates move apart from each other with gap filled by molten rock creating new crust
Rio Grande Rift East Africa Rift Mid-Atlantic Ridge Indian Ridge East Pacific Rise Indian Ridge separation marked by long mountain ranges on ocean floors and deep linear valleys (rift zones) on continents
convergent plate boundary plates move toward one another and where crusts of adjacent plates have different densities, denser plate is forced down or subducted beneath other
plate convergence with oceanic crust subducted beneath lower density continental crust plate convergence with oceanic crust subducted beneath oceanic crust plate convergence of continental crust against continental crust
marked by mountain belt or subduction zone with deep oceanic trench, volcanism and inclined earthquake (Benioff) zone
transform plate boundary plates slide past one another
crust neither created nor destroyed (earthquakes but no or extremely limited volcanism)
Plate boundary Characteristics Boundary Topography Igneous Metamorphic Sedimentary Earthquakes divergent-types ocean MOR basalt hydrothermal deep ocean shallow continent cont. rift basalt & rhyolite convergent-types continentcontinent low-t/low P mountains granites high-t/low P regional coarse clastics clastics shallow shallow intermediate deep continentocean volcanic arc & trench andesite high-p/low T regional clastics shallow intermediate deep oceanocean volcanic arc & trench andesite high-p/low T regional clastics shallow intermediate deep transform-types ocean very little none/limited basalt continent very little none/limited basalt none none shallow none none shallow intermediate