EAPS 11100 Lecture Notes - Lecture 11: Seafloor Spreading, Divergent Boundary, Convergent Boundary
19 Jun 2018
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LECTURE EXAM
Lec ⅔
1. What evidence led Geoscientists to conclude that the Earth’s surface was made of
distinct plates
a. The continents were originally believed to be 1 big continent. Evidence shows
that some continents have similar shapes and fossil records. Tectonic activity of
volcanoes and earthquakes caused this.
2. 3 types of plate boundaries and their description
a. Divergent: Plates move away from one another
b. Convergent: Plates move towards one another
c. Transform: Plates move horizontally past one another
3. Characteristics of 3 types of plate boundaries in terms of motions, tectonic activity, and
presence/absence of mountains
a. Divergent - EQV, magma fills plates, MOR occur shallow, beneath oceans mostly,
creates continental rifting, can lead to seafloor spreading, mountains
b. Convergent - EQV, creates subduction zones, mountains belts
c. Transform - EQ, MOR, spreading centers to make zigzag patterns (where 3 plates
meet is triple junction)
4. What does the orientation of volcanic island chains indicate?
a. Tectonic activities from volcanoes and EQ’s: island chains as a plate moves over a
hot spot. There are unusually high temperatures regions in the deep crust and
upper mantle.
5. Can you distinguish the different plate margins from map and elevation data?
a. Yes, topography is the top of the map while bathymetry is underneath the
ocean. You can see different depths and feature with the elevation data on a
map. In convergent boundaries you can see deep sea trenches. Divergent
boundaries usually occur in the ocean with higher elevation than seafloor.
6. What is convection and how does it work?
a. Movement caused within a fluid to cause hotter materials to rise and colder
materials to sink.
7. Why is convection relevant to plate tectonics?
a. W/o convection the magma inside the earth won’t flow, and the flow of magma
is what allows the plates to move, so then the whole plate tectonic process will
stop. TL;DR the motion causes plates to move.
8. Be able to identify and explain seafloor features and other tectonic elements on
continents and relate these to convection and plate tectonics.
a. Seafloor: seamounts and volcanoes
b. Seafloor features: Are not along plate boundaries but along hotspots. Midocean
ridges at divergent plates-magma moves up through the asthenosphere and
trenches at subduction zones when magma moves down.
9. Understand the details of subduction and seafloor spreading, in terms of large-scale
physical processes (i.e., convection).
a. Subduction: Occurs at convergent boundaries, 1 tectonic plate moves under
another tectonic plate and sinks into the mantle as the plates converge.
b. Seafloor spreading: Sometimes led to by divergent boundaries, the formation of
new areas of oceanic crust, which occurs through the upwelling of magma at
Midocean ridges over hot spots, seamounts, and volcanoes.
10. How (and why) do continents grow continuously larger through time while ocean basins
grow and shrink through the actions of plate tectonics?
a. Continents get bigger through the accumulation of volcanic material. Ocean
basins shrink because of divergent or convergent boundaries.
Lec ⅘
1. What is an earthquake? What are the different ways that seismic waves can be
generated (i.e., possible sources)?
a. A sudden or violent shaking of the ground, at times causing great destruction as
an indictment of movements within the earth’s crust or volcanic action.
Produced where there is a buildup of stress causing a fault and slip. Seismic
Document Summary
Lecture exam: what evidence led geoscientists to conclude that the earth"s surface was made of distinct plates, the continents were originally believed to be 1 big continent. Evidence shows that some continents have similar shapes and fossil records. You can see different depths and feature with the elevation data on a map. In convergent boundaries you can see deep sea trenches. Ocean basins shrink because of divergent or convergent boundaries. Produced where there is a buildup of stress causing a fault and slip. Seismic waves can be generated by volcanoes, magma, landslides, meteoroid impacts, and explosion: how do the location of earthquakes related to the 3 types of plate boundaries. How do earthquake depths differentiate them from others: earthquakes occur on plate boundaries. Most eq occur in narrow belts that coincide with plate boundaries. They happen in edges, mid-ocean ridges, subduction zones, and continental collisions. Deeper eq are located away from fault lines than shallow ones.
