NZ History I - Geology and Enviroments

What is the relationship between Gondwana and Zealandia?

- Gondwana spilt off from Pangea (supercontinent) 250mya

- Zealandia spilt off Gondwana 83mya

What is Zealandia?

- Mostly submerged contenient that contains NZ

- The continental crust of Zelandia is mostly too thin to go above sea lvl

- NZ is just the part of Zealandia that is sticking out of the water

^ bc of this NZ has gone through a lot of change due to sea level rise/fall (at one point 23mya it was nearly underwater)

Describe the fault line of NZ/Zealandia

- There is a fault line going diagonally along NZ

- In the North, the Pacific plate goes under the Australian Plate; in the South the Austrialian goes under the Pacific

(North = Australian plate on top; Australia is above NZ)

(South = Pacific plate on top)

- The fault line going diagonally in the South Island forms the Southern Alps becuase a covergent boundry (one goes under the other) has caused the earth to rise

Describe the plate tectonics of NZ/Zelandia

3 types of plate tectonics

- Divergent (plates drift apart from each other)

- Convergient (one plate goes under another/plates smoosh together)

- Transform (plates rub againest each other in antiparrell directions)

In NZ

- Covergiant caused the Southern Alps

- Transform causes lots of current earthquakes

Describe uplift vs erosion

- Uplift happens bc convergeint plate interactions

- Erosion is the natural weathering of rock, enviroment etc so that it is lower

Formation of the Southern Alps

On one side of the South Island (west coast) there is uplift caused by the Australian and Pacific plates colliding (convergent) = lots of rain

On the other side (Canterbury) there is erosion = warmer weather

- NZ's moutains are young = around 5mya

How did NZ's sea level change?

Low

- Global climate is cooler = more water in glaciers

High

- There are lots of glaciers on land, causing it to sink (NZ cold)

- Global climate is warmer = fewer glaciers (espically in antarctica) = more water in ocean = sea lvl rise

3mya melting of the Antarctic ice sheet increased sea levels around NZ

The last glacial max. (most water held in glaciers) was 2e^4ya; sea levels were more than 100m lower

NZ may have been entirely underwater 23mya (during the Oligocene) save a few islands which terristiral organisms were crouded on to

NZ's current coastline has been around for 8,000 years

Describe how lake Taupo's erruption changed NZ enviroment

- Lake Taupo had repeated, massive erruptions

- Was volcanically active for 1.6my

- Had a MASSIVE erruption 26,500 ya

- Covered clostest regions in 3m of ash

- Killed all vegiation in central NZ

- Caused a crater (lake Taupo) and also for the collapse of earth around it

What are the 3 main theories about how organims got to NZ?

Contenential drift

- All the flora & funa in NZ evolved from that in Gondwanan

Land bridges

- Sea level changes exposed land that allow species to move between islands/places near NZ too NZ, these species then evolved

Transoceanic disperal

- Flying, floating etc

- Easy for birds but for (eg) native frogs islands inbetween would be needed

What speices may have Gondwanan origin?

- Moa

- Kiwi

^ both in the group ratities (which is Gondwanan) but their origins are more recent

- Velvet worms

- Tuatara

-Leiopelmatid frogs

- Bats

It is hard to prove the origin of species (easy to prove where they're not from; hard to prove where they are)