Week 3 - Earth Processes Flashcards
How is the earth structured vertically and horizontally?
How do tectonic plates move, and at what rate?
They move 1 - 20 cm year
They slide along weak asthenosphere (just below lithosphere)
Driven by gravity, linked to convection mantle
Continents are carried passively by plates
How do individual tectonic plates differ from one another?
What are the different types of plate boundaries? What sort of features are found at each?
Divergent - Plate margins pull apart from each other < >
Convergent - Plate margins move towards one another. > <
Transform - Plate margins move sideways past each other ^
Where do earthquakes occur, and why?
Along plate boundaries due to faulting.
FAULTING
- tectonic forces can cause rocks to break
- fractures in rocks across which rocks on each side have been displaced
- can be NORMAL under extension (block drops down, no overhang) or REVERSE under compression (block pushes up, overhang)
- other faults can be strike-slip, where the two sides laterally pass each other
- fault movements cause earthquakes
How does a fold differ from a fault?
FOLDING
- plate convergence compresses the crust and folds rock strata
- they can be synclines, where the limbs turn upwards or anticlines where the limbs fold downwards
- produces fold belts where the land surface is buckled into linear anticlinal ridges
FAULTING
- tectonic forces can cause rocks to break
- fractures in rocks across which rocks on each side have been displaced
- can be NORMAL under extension (block drops down, no overhang) or REVERSE under compression (block pushes up, overhang)
- other faults can be strike-slip (transform), where the two sides laterally pass each other
- fault movements cause earthquakes
What are the differences between volcanic and tectonic landforms?
What does Earth Systems consist of?
- Atmosphere
- Landforms (Lithosphere)
- Oceans and Rivers (Hydrosphere)
- Organic component (Biosphere)
They interact via processes and energy flows
e.g. gravity, solar energy, humans
What are Landforms?
Landforms are the dynamic outcomes of processes of the Lithosphere in combination with the hydrosphere, atmosphere and biosphere. The features of landform reflects the dominant geomorphic process.
Landforms are the surface features that make up the continental landscapes.
Many large scale features e.g. mountain ranges, river systems are associated with present or past plate boundaries
Other landforms are found within plate interiors
What is a Landform pattern?
Defined as a set of clearly reoccurring morphological features in the landscape over a circular area of 300m - 500m radius approx.
What are Landform elements?
Are assessed at the detailed scale with a radius of 20m
What are initial landscapes?
Initial landforms are constructional features produced either by VOLCANIC PROCESSES or PLATE BOUNDARY (tectonic) FORCES
What is the Earth Crust made of?
Core
Mantel - mostly solid, weak melt, creeps slowly by convention currents
Crust - Continental (thicker) and Oceanic (thinner)
What is the theory of Plate Tectonics?
Three major concepts:
- Lithosphere broken up into number of rigid segments called plates
- Plates constantly moving relative to each other
- MAJOR STRUCTUAL FEATURES of the Earth are formed from processes occurring at plate boundaries
What is the process of Mantel Convection?
Name the 7 Lithospheric Plates
- Pacific
- Eurasian
- Australian-Indian
- North American
- South American
- African
- Antartic
How do Plates move?
They move 1 - 20 cm year
They slide along weak asthenosphere (just below lithosphere)
Driven by gravity, linked to convection mantle
Continents are carried passively by plates
Describe Divergent plate boundaries
Plate margins pull apart from each other
New crust is generated to fill the gap
Examples: Oceanic Ridges and Continental Rift Zones
< >
Describe seafloor spreading
Seafloor spreading explains how the oceans grow by generating new crust along the oceanic ridge.
New floor is produced by continual volcanic activity along the crest of oceanic ridge
Magma from asthenosphere rises to fill the gap
Describe Convergent plate boundary
Plate margins move towards one another. ><
*oceanic crust is being subducted under continental crust, giving rise to volcanoes at boundary
E.g. Nazca plate
Three types:
1. Continental Arc
2. Island Arc
3. Continental collision zones
Describe Convergent plate boundary
Plate margins move towards one another. >< Three types: 1. Continental Arc 2. Island Arc 3. Continental collision zones
What are subduction zones/orogens?
They mark sites where old oceanic lithosphere dives back into the mantle
Marked by paired oceanic trenches and volcanic arcs
Become regions of mountain building - initial landscapes
They are sites of intense earthquake activity, volcanoes, sedimentation, deformation and metamorphism
May lead to continental collision zones
Describe Transform Plate Boundary (conservative plate boundary)
Plate margins move sideways past each other
The lithosphere is neither consumed nor generated
Example: San Andreas Fault California , Alpine Fault NZ, Dead Sea Transform
Transform faulting - is a strike-slip fault occurring at the boundary between two plates of the earth’s crust.
