PLATE TECTONIC SUPERCYCLE: What effect does the plate tectonic…
PLATE TECTONIC SUPERCYCLE:
What effect does the plate tectonic supercycle have on earth?
SUPERCONTINENTS & SUPERCYCLES
the process of earth’s land masses forming a single supercontinent, then breaking apart into smaller landmasses and then back again into one landmass.
cycle the earth goes through in a period of 400-600 million years.
Plate Tectonics results in the formation of supercontinents, when many of the Earth’s landmasses collide together. Later, new rifting causes fragmentation & separation into more, smaller continents. These may later re-combine in a totally new arrangement. The complete cycle takes 300-500 Ma.
The “cratons” or continental “shields” are almost indestructable pieces of continental lithosphere. These may survive many supercycles.
e.g of supercontinents: Rodinia, Pangea,Laurasia,Gondwana
another supercontinent likely to form in around 250million years
PLATE TECTONICS AND GLOBAL CLIMATE
less rifting & volcanic activity. Lower CO2 levels lead to greenhouse cooling. Lower temperatures mean less evaporation so there is less precipitation, so drier climates.
world climates become generally colder & drier.
When the climates are colder, the formation of permanent ice-caps withdraws water from the oceans, so sea levels are lower.
desert environments & tundra at higher altitudes
ageing ocean basins are lower, deeper bowls which hold more water. This has the effect of lowering sea levels.
many, smaller continents.
more rifting and seafloor spreading occurring. The extra volcanic activity raises CO2 levels. Greenhouse warming produces hotter, wetter climates.
climates tend to be warmer & wetter.
Hotter climates are unlikely to have ice-caps, so sea levels are higher. Also more evaporation and precipitation
Rainforests & temperate forests at higher altitudes. Also shallow seas create coral reef ecosystems
young ocean basins are shallower. This “pushes” sea levels higher.
volcanic eruptions can influence the weather when their dust clouds obscure the sun, reducing the amount of sunlight reaching the earth's surface
ocean currents allow for mixing of waters and the transfer of heat around the earth. when equatorial current is prevented, it results in an ice house world.
IMPACTS ON EVOLUTION OF LIFE
many, smaller continents
The rate of evolution seems to speed up when
there are many, smaller continents
More, smaller continents tends to result in a greater variety of habitats on both land and sea. This creates more opportunities for the evolution of new types which leads to greater diversity.
Rate of evolution slows down
when there are fewer, larger supercontinents.
slower rates of evolution and less diversity. This is because more landmasses are at the same latitude and have more similar climates.
alignments in a north-south direction have a greater range of latitudes & possible climates. This favours faster evolution & greater diversity.
Higher levels of mountain building tend to produce greater diversity. Each mountain presents a range of altitudes resulting in many more habitats for life. This increases the overall rate of evolution of diverse types.