Download natural environments study notes large scale earth processes

NATURAL ENVIRONMENTS STUDY NOTES
LARGE SCALE EARTH PROCESSES
Earth’s Interior
Closed matter system: a physical
system where matter doesn’t cross the
boundaries
• Water cycle, nutrient cycles –
nitrogen, phosphate
Open matter system: a system where
matter can cross boundaries, + has
external interactions
• A farm, a city
Attributes: physical objects of an
environment (features)
Process: natural forces, which form,
shape or reshape an environment
Interaction: between attributes +
processes
Plate Tectonic Theory (3 major concepts)
Crust Type
Age
Density
1. Lithosphere is divided into rigid segments – plates
Oceanic
Younger More
2. Plates are constantly moving in relation to each other
dense
3. Major structural features of the Earth are made by
3.0g/cm3
processes at plate boundaries
Continental
Older
Less
• Major plates: Pacific, Eurasian, Australian-Indian,
dense
2.7g/cm3
African, Antarctican, north American + south American
• Plate motion: 2-10cm/y – slide across Asthenosphere driven by gravity (ridge pull/slab
push) and convection currents in the mantle
Depth
Thinner
5-10km
(a:7)
Thicker
25-50km
(a:35)
Plate Boundaries
Boundary
Divergent
Convergent
Conservative
Movement
• Plates move away from each other
• New lithosphere formed from magma
pushing through gap
• Plates collide with each other
• Lithosphere is consumed – sites of
intense earthquakes, volcanoes and
metamorphism
• Lithosphere neither created nor
destroyed
• Plates slide past each other along faults
Features
Mid Oceanic Ridges (Sea
Floor Spreading)
Rift Valleys
Subduction Zones
Mountain building
(orogenies)
Example
Mid-Atlantic Ridge
Great East African Rift
Valley
Andes (O-C)
Himalayas (C-C)
Mariana Trench (O-O)
Earthquakes
Volcanoes
Alpine Fault
San Andreas Fault
EARTH MATERIALS
Create landscapes across the world
Chemical composition of earth materials affect stability +
weathering of certain landscapes
•
•
Minerals
Major solid constituents of Earth
Specific physical properties reflect composition + atomic
structure à affect weathering
95% Earth’s crust = silicates
•
•
•
•
•
•
Minerals: naturally occurring
inorganic chemical compounds
with specific internal structure +
chemical composition
Rocks: natural mixtures or
aggregates of minerals
Silica Tetrahedron
− Olivine
Silicates
Combine oxygen + silicon with other minerals
Made of 1 silicon + 4 oxygen in a tetrahedral arrangement
Have the ability to polymerise (bond out into rings, chains,
sheets or frameworks)
Single Chain
− Pyroxene
Double Chain
− Amphiboles
Sheet
− Mica
Framew ork
− Quartz, Feldspar
Rock Classification
IGNEOUS
• Formed by solidification of molten rock
o Extrusive (Volcanic): cools rapidly at surface, fine grained
crystals, glassy
o Intrusive (Plutonic): crystalise slowly below surface, coarse
grain crystals
• Composition = mainly silicate minerals
o Felsic: light colour + low density (Feldspar + Quartz à
framework)
o Mafic: dark colour + high density (Mica à sheet, Pyroxene
à chain)
Intrusive
Granite
Extrusive
Rhyolite
Felsic/
Mafic
Diorite
Andesite
Mafic
Gabbro
Basalt
Felsic
Origin of Magma
• Most originate at depths of 50 – 200km (Asthenosphere)
• Basaltic: generated by partial melting of ultramafic rocks in the
Asthenosphere
• Granitic: partial melting of rocks in the upper crust
SEDIMENTARY
• Are aggregates deposited by transporting medium (wind, water,
ice), or deposits of organic origins, or chemical precipitates
• Common Minerals: quartz, clays + carbonates
• Form in layers (Strata)
Dykes: igneous intrusion
vertically – magma solidified in
fractures
Sills: igneous intrusion
horizontally – sheets of solidified
magma