Lecture 11 Flashcards
1
Q
What are the 3 major topographic units of the ocean floor ? (CmDb,Mr)
A
- Continental margins
- Deep-coean basins
- Mid-ocean ridges
2
Q
Types of continental margins ?
A
- Active and Passive
3
Q
Passive continental margins ?
A
- Found along coastal areas that surround the Atlantic ocean.
- Not associated with plate boundaries
- Experience little volcanism and few earthquakes
4
Q
Continental shelf of the passive contiental margins ?
A
- flooded extension of continent
- varies greatly in width (80km)
- Gently sloping submerged surface
- Contains important mineral deposits
- Areas mantled by extensive glacial deposits
5
Q
Continental slope of the passive continental margins ?
A
- Marks seaward edge of continental shelf
- Steep feature (5 to 25 degree slope)
- Boundary between continental crust and oceanic crust
- True edge of continent
6
Q
Continental rise of the passive continental margins ?
A
- Continental slope that merges into a more gradual incline
- Can extend for 100 km.
- Thick accumulation of sediment
7
Q
Active continental margins ?
A
- Continental slope descends abruptly into a deep-ocean trench
- Around Pacific Ocean
8
Q
How accretionary wedge is formed ?
A
- Accumulations of deformed sediment and scraps
9
Q
How knowledge of mid-ocean ridges comes from ?
A
It comes from soundings, core samples, and visual inspection by submerisbles.
10
Q
How Mid-Ocean Ridges are characterized by ?
A
- Elevated position
- Extensive faulting
- Numerous volcanic structures that have developed on newly formed crust
11
Q
Rift valleys ?
A
Deep, down-faulted structures along axis of segments
12
Q
By what seafloor spreading is characterized ?
A
Frequent, weak earthquakes
13
Q
Layers of structure of the oceanic crust ?
A
- Upper layer : Pillow lavas
- Middle layer : Interconnected dykes called sheeted dykes
- Lower layer : Gabbro, in a sequence of rocks called ophiolite complex
