Chapter 1 - Earth's Dynamic Surface Flashcards
“Deep Time”
Geological time scale
How old is the Earth?
4.6 billion years
When life first appeared on Earth
3.5 billion years
Light Switch Theory
570 million years ago. An acceleration in an abundance in life attributed to the evolution of eyes
Anthropocene Epoch
New epoch defined by human impact on the Earth (identified by a radioactive signature). First nuclear explosion on July 16th 1945 at 5:45
Anthropocene Epoch
New epoch defined by human impact on the Earth (identified and dated by a radioactive signature). First nuclear explosion on July 16th 1945 at 5:45
Geomorphology
The study of the features on the Earth’s dynamic surface, their history and the processes that create them.
Geological Features
- Landscapes
2. Landforms
Landscapes
Larger scale feature that includes a number of different landforms (i.e. rivers system)
Landforms
Smaller scale feature, a natural feature of the earth’s surface. (i.e. point bar)
Tectonics
Movement of the Earth’s lithosphere
Endogenic
internal, generated from within
Exogenic
External, generated from the outside
Exogenic processes are driven by….
The Sun’s energy and the temperature gradient between the poles and the equator
Three systems we study in geomorphology
Geosphere
Hydrosphere
Biosphere
Geosphere
the rocks comprising the Earth’s crust and the global tectonic system that elevates the rocks that get sculpted into the topography
Isotasy
the equilibrium that exists between parts of the earth’s crust, which behaves as if it consists of blocks floating on the underlying mantle, rising if material (such as an ice cap) is removed and sinking if material is deposited.
Asthenosphere
the upper layer of the earth’s mantle, below the lithosphere
- the part of the mantle which is not solid. a semi liquid
Example of Isostatic compensation
for example, as the surface of a mountain chain is eroded over the years, the crustal root rebounds and uplift occurs.
Example of Isostatic compensation
for example, as the surface of a mountain chain is eroded over the years, the crustal root rebounds and uplift occurs.`
Lithosphere
the rigid outer part of the earth, consisting of the crust and upper mantle.
Types of tectonic boundaries (plate margins)
Where plates meet
3 TYPES:
- Convergent
- Divergent
- Transform
Convergent boundary
Plates collide head on
Divergent boundary
Plates are moved apart
Transform boundary
Where plates are moving past each other in a side to side motion
Rock Types:
Igneous
Sedimentary
Metamorphic
IGNEOUS ROCKS
Rocks formed directly from the cooling of magma
(e.g. basalt, granite).
SEDIMENTARY ROCKS
Rocks formed from layers of debris compacted and lithified
(e.g. sandstone, mudstone, limestone,
Halite).
METAMORPHIC
Rocks whose minerals have become unstable in their environment and are changed into something new
(e.g. slate, schist, gneiss, and marble)
Geomorphology draws on 4 different disciplines…
chemistry, biology, physics, geology
Hydrosphere
oceans, atmosphere, and surface and subsurface waters that erode, transport and deposit sediment
Earth’s lithosphere is divided into ___major & several minor
plates
Earth’s lithosphere is divided into 7 major & several minor
plates
Four processes responsible for landform development (4)
MOVING WATER
MOVING AIR
MOVING ICE
GRAVITY
Sediment
Fragments of rocks found on the Earth’s surface
Why is sediment important
Provides us with a record of previous environments because:
- It is found in almost al environments on the Earth’s surface
- It records information about the environment in which it is found. (through weathering, transport, erosion, deposition)
- It contains evidence of life forms in the form of living and dead organisms (fossils)
- Sediment (and sedimentary rock) is found throughout the rock record)
All systems try to reach an _______
equilibrium
The geomorphology of Canada is dominated by….
glacial land forms left behind by glaciers and the last ice advance and retreat
2 basic forces responsible for land form development
Gravity
Friction
Sedimentary Texture
Refers to the physical characteristics of individual sediment grains.
Sedimentary Texture
Refers to the physical characteristics of individual sediment grains.
Roundness
A measure of how smooth or rough the surface of a grain is.
Sphericity
A measure of how spherical a grain is. It is a measure of the shape of a grain.
Sorting
The range of grain sizes in a sediment deposit.
(Sedimentary Texture) Types of physical characteristics
- Grain Size
- Roundness
- Sphericity
- Sorting
(Sedimentary Texture) Types of physical characteristics
- Grain Size
- Roundness
- Sphericity
- Sorting
Rocks and minerals often have ___ common colours
- Black/dark
2. White/light
Black/Dark rocks and minerals are typically
Mafic.
Higher density.
White/Light rocks and minerals are typically
Felsic.
Lower density.
Minerals will sometimes separate (move differently) because of differences in d_____
Minerals will sometimes separate (move differently) because of differences in density.
Sedimentary Structure
A physical feature in sediment present because of a preferred arrangement of grains.
Why is there turbulent flow?
Friction
Vegetation zones (5)
- Grassland
- Temperate Forests
- Tropical Forest
- Desert/Arid
- Polar
Geological characteristics of a GRASSLAND
- Most of the biomass is underground.
- Dense root mass binds the sediment and soil together.
Geological characteristics of a TEMPERATE FOREST
- Large amounts of biomass are found above and below ground.
- While sediment and soil are bound together the biomass
above ground adds a significant amount of weight and possibly organic sediment.
Geological characteristics of a TROPICAL FOREST
- Most of the biomass is above ground.
- There tends to be a shallower root zone.
- Soil and sediment is less cohesive and more prone to erosion once vegetation is removed and the ground is exposed.
Desert/Arid
- Vegetation is often minimal (small and sparse)
- In this case even a small, isolated obstacle such as a plant can significantly affect sedimentary processes.
Weathering
The disintegration of rocks and other minerals by physical and chemical means.
Erosion
How sediment is set in motion.
Transport
How sediment moves once it is set in motion.
Deposition
How sediment stops moving.
Precipitation
The formation of new mineral crystals from elements in solution
Two basic forces responsible for landform development.
- Gravity
2. Friction
Talk about the effect of small vegetation in an arid/desert zone
Will change how sediment is distributed. Deposition on the the downwind side, erosion on the upwind side as flow and velocity changes around the plant.
All vegetation will act to trap ______
sediment
Polar conditions
In northern Canada this includes freezing and thawing conditions.
Polar conditions in the winter
Snow moves across the surface because of wind. In the presence of vegetation. In the presence of vegetation snow will accumulate on the ground.
Snow on the surface acts as an insulator preventing the ground from freezing or at least not freezing as much.
Polar conditions in the summer
In summer the ground that was covered with snow undergoes more thawing while the area not covered in snow during winter is less thawed.
Therefore the area originally covered by snow in winter - because there was more vegetation - is more prone to erosion in the summer.
Active Layer
the layer on permafrost that is subject to thawing.
Basic Principles
- Uniformitarianism
- Actualism
3.
Uniformitatianism
The same processes operating on the Earth’s surface have been operating since the beginning of the Earth. These processes are generally slow. These processes should continue unchanged into the future.
The earth is very old.
Actualism
The Earth operates, has operated and probably will continue to operate by slow, consistent processes that are periodically interrupted by catastrophic events.
