Chapter 13: Tectonics, Earthquakes, and Volcanism Flashcards
Define relief and explain the difference between the three orders of relief. How does topography differ from relief?
- Relief is elevation differences in a local landscape; an expression of height difference between landforms
-First order - coarsest level (biggest); concerns continental land masses and ocean basins
-Second order - middle level; concerns mountain ranges, plains, lowlands, mid-ocean ridges, oceanic trenches - Third order - most detailed; concerns individual mountains and cliffs, valleys, and hills
- topography - undulations and other variations in the shape of earth’s surface
Describe the six types of topographic regions. Where on the planet does each type dominate?
1.) plains - extensive, the local relief is greater than 100 m
- dominates: North & South America, Asia and Australia
2.) High tablelands - elevated, have either flat or gentle slope in surfaces; elevation: less than 1520 m, and local relief: more then 300 m
dominates: Colorado Plateau, Greenland and Antarctica
3.) Hills and low tablelands - elevation: less than 100 m, local relief: greater than 600 m
-dominates: Africa, part of Europe, Australia
4.) Mountains - steep slopes, formed by tectonic processes; local relief: less than 600 m
dominates: every continent
5.) widely spaced mountains - isolated, local relief: more than 150 m
6.) depression - surrounded by mountains, hills, or tablelands
-dominates: Asia and Africa
What information can be gleaned from the hypsographic curve?
-It shows us distribution of Earth’s surface by area and relative elevation to mean sea level
Explain the processes that form new crust. Where is the oldest and youngest crust found in Canada?
-Tectonic activity (powered by internal activity (from earth’s core))
- Weathering and erosion - (powered by sun through motion of air, water, and ice)
-Oldest crust is found in the Canadian Shield
-Youngest is in the western coast, areas adjacent to pacific ocean
Define terrane and explain the process of accreted terranes. Where has this occurred in North America?
- Terrane - A migrating piece of Earth’s crust, transported a distance by the process of plate tectonics.
- Process: Slowly migrating fragments of the ocean floor, arcs from volcanic islands, and pieces of crust from other continents over time, have all been forced against the edges of continental shields and platforms and become accreted to the plates.
-Wrangell mountains and Valdez, Alaska
Explain the difference between stress and strain. Name the three types of stress and describe and name the various types of crustal deformation that result from each (folding and faulting).
Provide examples of places in the world that exhibit such deformation.
- Stress is something rocks get subjected to due to tectonic forces, gravity, and pressure from overlying rocks
- Strain is how rocks tend to respond to stress, and it results in rocks folding(bending) or faulting (breaking)
-3 stress types:
- Tension - causes stretching strain (thinning crust, normal fault)
-Compression - causes thickening and shortening (folding, reverse fault)
-Shear - causes twisting laterally (bending horizontally, strike slip fault)
Folding ex. in world : The folded mountains in the Zagros Crush Zone, Iran
Faulting ex. :Canyonland’s National Park, Utah - faulted landscape
What is a recurrence interval with respect to fault movements? When was the last time there
was a large earthquake along the subduction zone off the west coast of British Columbia, and
when might we expect the next one (see your textbook readings)?
-It’s the average time interval that occurs between two recorded events of seismic activity (created by earthquakes) of equal magnitude along the same fault.
-last significant earthquake along the subduction zone in BC was in the early 1700s
-it’s estimated recurring interval for earthquakes along Cascadia subduction zone is about 300-600 yrs
-might see next one happen sometime within the next few centuries
