Plate Tectonics Flashcards
Geologic Cycle
Geology, topography and climate influence the type, location, and intensity of earth processes.
Materials at or near Earth’s surface have been continuously created and modified by various physical, chemical. and biological processes: these processes constitute the geologic cycle.
The geologic cycle consists of a group of sub-cycles: the tectonic cycle; the rock cycle; the hydrologic cycle; and biogeochemical cycles.
Tectonic Cycle
Tectonic activity refers to large-scale earth processes that cause the movement and deformation of Earth’s lithospheric plates.
These processes create landforms and landscapes at a variety of spatial scales (e.g., orogenic mountain ranges and ocean basins to individual faults.)
Endogenic Processes
Tectonic process are driven by energy generated deep within Earth: original heat of formation of the planet, heat generated by crystallization of the core, and heat supplied by radioactive decay of elements in the mantle.
Rock Cycle
Rocks are aggregates of one or more minerals.
Minerals are naturally occurring crystalline materials with specific chemical compositions and a narrow range of physical properties.
Links to endogenic processes and exogenic processes driven by energy from the sun.
Three Classes of Rock Are
Igneous
Sedimentary
Metamorphic
Internal Structure of The Earth
Internal structure based upon: chemical composition of rock; physical state - solid vs. liquid; density; and rock strength.
Solid inner core, liquid outer core, and solid mantle.
Inner Consists Of
> 1300 km thick
Extremely hot temperatures
primarily metallic; consists mostly of iron (Fe) with minor amounts of nickel (Ni), sulphur (S), and oxygen (O)
Liquid Outer Core Consists Of
Over 2000km thick
Composition close to the inner core.
Movement within the outer core generates Earth’s magnetic field.
Solid Mantle
~3000km thick
Composed largely of iron (Fe) and magnesium (Mg) - rich silicate minerals - ferromagnesian minerals.
What is the lithosphere?
Cool, strong outermost layer of Earth
Crust + Rigid uppermost portion of mantle
Varies in thickness: few km beneath mid-oceanic ridges
Asthenosphere
Lithosphere overlies asthenosphere, a mass of hot, relatively weak rocks (magma) capable of slow movement.
convection operates to move material within the mantle; convection is driven by heat from Earth’s core
Plate Tectonics
Lithosphere is broken into larger and smaller pieces call lithospheric plates.
Plates may include a continent and parts of ocean basins, or may be restricted to only ocean basins.
Plates move relative to one another at rates of several cm per year.
Processes involved in the creation, movement, deformation and destruction of plates are collectively known as plate tectonics.
Continental Drift Theory
developed by Alfred Wegener in 1912.
Coastline fit - Southern Hemisphere continents
Similarities in Paleozoic geology and palaeontology
Single Continental Landmass - Gondwanaland
Theory lacked a convincing mechanism capable of moving continents
Who discovered the seafloor spreading and subduction?
American Harry Hess and Japanese Kiyoo Wadati and American Hugo Benioff in the 1950’s and 1960’s
Mid Oceanic Ridges are associated with what natural disasters?
Spatial patterns of earthquakes and volcanism
Oceanic Trenches are associated with what natural disasters?
Spatial pattern of earthquakes in Wadati-Benioff zone and Volcanism along continental margins.
Plausible mechanism for continental drift?
Seafloor spreading
Geomorphology
refers to the study of the morphology of the surface of the Earth and the processes operating on it, in the present, past, and the future
The morphology of the Earth’s surface is created by the constant interaction of endogenic processes, those processes that create topographic relief, and exogenic processes, those processes that reduce topographic relief.
Physical/ Environmental Controls to Earth Processes to Landforms to Landscapes.
Geomorphology seeks to
understand the sequence of landscape development
understand the dynamics of physical, chemical, and biological processes that create landforms
predict the nature of future change based on field observations, physical experiments, and numerical modelling
Structure
Bedrock structure influences physiography
Tectonic Geomorphology
Structural geology, geophysics, geodesy
History
Sequence of landscape development
Historical Geomorphology
Stratigraphy, palaeontology, archaeology, pedology.
Processes
Endogenic vs. Endogenic processes that affect landforms (driving forces)
Process Geomorphology
Geography, Sedimentology, Engineering
Earth Materials
Strength and resistance of rocks and sediments (resisting forces) - geology engineering
Tension
Lithospheric plates are pulled apart - divergent plate boundaries.
Compression
lithospheric plates are pushed together - convergent plate boundaries
Lateral Movement
Lithospheric plates move horizontally past each other - transform plate boundaries
Landscapes of Tension
Landscapes marked by tension, crustal extension, and the failure of brittle rock units are dominated by normal faulting.
These processes occur at mid-oceanic ridges (spreading centres) and contribute to seafloor spreading.
Normal Fault
Rocks fail along a steeply inclined surface, typically sloping at the angle of between 45 degrees and 70 degrees.
Rift Valley
When two normal faults sloping in opposite directions create a rift valley that flanks a structural depression termed a graben.
How do mid-oceanic ridges form?
Where magma from the mantle rises and is erupted as pillow lavas forming broad ridges with a central rift valley where plates break apart and move apart.
New formed oceanic lithosphere composed of?
Basalt and Gabbro, moves away from the ridge crest.
Convergent Plate Boundaries (3 types)
Oceanic - Continent Collision
Oceanic - Oceanic Collision
Continent - Continental collision
What are the results of compression?
shortening of the lithosphere, a combination of folding and faulting, resulting in an increase in elevation and thickening of the lithosphere – creates orogenic mountain chains
What does compression do offshore?
offshore, subduction of oceanic lithosphere creates deep, narrow depression in the seafloor – an oceanic trench
Cuesta
ridge composed of sedimentary bedrock, where one side dips at a gentle angle and the opposite side forms a steep escarpment.
Features in landscapes marked by compression include:
Rock units include folding and reverse (thrust) faulting
Folded terrains are caused by
alternating of down-warped synclines and up-warped anticlines - often leading to the development of ridges (anticlines) and valleys (synclines)
Cuesta
Ridge composed of sedimentary bedrock, where on slide dips at gentle angle and the opposite side forms a steep escarpment
Reverse Faults
Move rocks on the upper side of the fault (called the hanging wall) up and over those on the underside of the fault (the footwall)
Thrust Faults
most common class of reverse faults, involving movement over gently inclined surfaces.
thrust-faulting is characteristic of compressive terrain associated with subduction zones.
How are rock units split?
Horizontally by transform (or strike-slip) faults and displaced laterally.
A clean break results in no difference between the two blocks.
More commonly, the moving blocks are forced into contact, fracturing rock faces and grinding the contact surface under high pressure.
Transform Faults
are most common on the ocean, but some occur on continents; e.g., San Andreas Fault in California, Queen Charlotte Fault west of Haida Gwaii
Canadian Shield
Created between 1.96 and 1.81 billion years ago through the collision and welding together of at least six ancient microcontinents.
Divided in structural provinces consisting largely of Archean granite (igneous) and gneiss (metamorphic) rocks, welded together by orogenic mountain belts consisting largely of Late Proterozoic volcanic and metamorphosed sedimentary rocks.
Landform comprising the exposed part of the North American craton.
Craton
Refers to old continental crust preserved deep within the centers of continents.
North American-craton
Large continent-sized block of Archean and Proterozoic rock stretching from Mexico to USA, Canada, and Greenland
Canadian Shield
Physiographic Region Characterized by:
Rolling topography (local relief between 60-90 metres)
Product of weathering and erosion over long periods of geological time. (i.e., 100’s million years)
Present topography influenced by Pleistocene glacial erosion; a lake-studded landscape.
Appalachian Mountains
Rock range in age from the Precambrian to the Mesozoic
mountain building was associated with the opening and closing of the Iapetus Ocean
Appalachian Mountains
Closure of the Iapetus Ocean was associated with…
Subduction of oceanic lithosphere and extensive volcanism; an ocean-continent collision
Appalachian Mountains
Closure was terminated by
A Continent to continent collision accompanied by folding, thrusting, and metamorphism of sedimentary rocks along the continental margin.
Appalachian Mountains
In the early Mesozoic _______ along the eastern border of this mountain system was associated with the creation of the Atlantic Ocean Basin
Continental Rifting
Canadian Cordillera
this region includes the mountains of British Columbia, Alberta, Yukon, and Northwest Territories
these mountain ranges have resulted from plate collision and crustal shortening
the eruption of basaltic lavas, the construction of composite volcanoes, the intrusion of granite batholiths, and the folding and overthrusting of continental lithosphere have accompanied ocean-continent collision during the Mesozoic and Cenozoic
Innuitian Mountains
this region of Canada experienced rapid deposition of sedimentary rocks and continuous subsidence throughout the early Paleozoic (Cambrian-Devonian)
orogeny in the Late Paleozoic (Devonian-Carboniferous) involved the eruption of basaltic lava and the folding and faulting of the overlying sedimentary rocks
further uplift of the region was associated with the emplacement of granite batholiths (epeirogeny)
subsequent weathering and erosion (Carboniferous-Cretaceous) heralded the return to rapid sedimentation and subsidence
orogeny in the Early Paleogene involved the uplift, folding and faulting of the sedimentary rocks and the intrusion of igneous dykes.
Plate Tectonics and Hazards
earthquakes and volcanic eruptions threaten human populations living near lithospheric plate boundaries
tsunamis are generated by subduction-zone earthquakes
landslides and snow avalanches occur most commonly in mountains produced by lithospheric plate collisions
