LECTURE 19- NZ Geological and Biological History

what is a divergent boundary (plates)

plates go in opposite directions and move apart to allow magma to reach surface (causes volcanoes)

what is a convergent boundary (plates)

one plate is on top while the other is underneath

what is a transform boundary

 plates slip sideways against each other

when did Zealandia begin to break away from Gondwana

83 million years ago

where did the oceanic crust form

Tasman sea over a period of 30 million years

what is the relationship between Aotearoa and Zealandia

Aotearoa is now considered to be the exposed portions of an otherwise submarine continent Zealandia

what plate are the North Island and and top of the south island on

Australian plate

what plate is the south island on

pacific plate (slid into place to form NZ)

how did aotearoa form from plates

Aotearoa formed at the junction the australian (west side) and pacific plates (east side)

what happened to Aotearoa during the Oligocene period

Most of Aotearoa (almost all) was submerged during the oligocene epoch (33.9–23.03 million years ago)

known due to limestone deposits along mountain ridges (that forms underwater from shellfish)

what is mountain uplift

Uplift from geological forces causes land to rise, while erosion will cause land to go down

• formed Aotearoa’s landscape

how does plates colliding cause mountains to form

australian and pacific plates slowly moving together, causing pressure and land slippage

• caused the alpine fault in the south island that formed the southern alps

how does volcanism form mountains

many active volcano fields in NZ. eruptions can send out ash and flatten surrounding landscape, and kill vegetation and life

what happened to NZ during the late pliocene 3 million years ago

the melting of the antarctic ice sheet increased sea levels around New Zealand

what was NZ’s landscape like 100 million years ago

new zealand basement rocks- old ancestral rocks with new mountains forming

what was NZ’s landscape like 70 million years ago

 mountains wear down, land is opening up, sea is reaching around edges

what was NZ’s landscape like 30 million years ago

 land is slow, erosional sediments, and ocean over most of land with small island remaining

what was NZ’s landscape like 25 million years ago

change in tectonic regime causing south island moving into place, volcanism, and pressure from plates forcing land upwards and new mountains forming

what happened to NZ’s landscape during the last glacial maximum (20,000 years ago)

Sea levels were >100m lower, and NZ was one big landmass. glaciers affected vegetation

when did the drowning period in the oligocene occur

25 million years ago

when did mountains form through uplift and volcanism

5 million years ago

when did warm and cool periods affecting sea levels occur

2.6 million–12,000 years ago

how did NZ obtain its flora and fauna

1. Continental drift (before 83mya)

2. Land bridges (Zealandian islands)

3. Transoceanic dispersal (flying, floating)

what NZ flora have vicarant (gondwanan) origins

Beach forest (Nothofagus): Gondwanan group of plants

what species in NZ have vicarant (gondwanan) origins

1. Peripatus “Velvet worms” (85-94mya)

2. Leiopelmatid frogs (hamilton’s frogs) (67–130mya)

3. Tuatara (100–130mya)