Schol GEOLOGY Flashcards
General law of superposition
Sediment forms layers, oldest at the bottom
Folds and faults disrupt the law
Describe igneous intrusion
Magma penetrates existing rocks and solidifies, forming a sill
Describe igneous extrusion
Magma flows out onto the surface as lava, or pyroclastic rock ejected by a volcano
Become embedded into the rock strata with continued deposition
How can igneous intrusions and extrusions be identified
Identified by CRYSTAL SIZE, determined by how fast it cools
Intrusion > extrusion
Cools SLOWER = LARGER crystals
what are unconformities?
buried surface where no deposition occurred or was eroded away before the next deposition.
break in geological record
ways to correlate data (rocks)
matching similar rock layers
using index fossils
ashfall from volcanic events
tephrochronology
ash (tephra) from a single event has unique chemical properties so it can be identified
tephra horizon acts as a time marker in rock strata
what is geomorphology?
factors
a study of the origin and evolution of surface features.
factors:
Aeolian, hydrologic (fluvial, standing water), glacial, mass wasting, igneous in/extrusion, tectonic
astrogeology
study of solid bodies in the solar system, comparing geological features w/ evolution of earth
Aeolian processes
give an example in astrogeology
wind-driven.
erosion/deposition.
dune formation and erosion on Earth shows prevailing wind strength and direction, and general atm conditions.
–> compare to dunes on Mars, both modern and lithified.
hydrologic processes
identifying valleys, channels, shorelines, deltas.
have been identified on Mars.
Glacial processes
abrasive flow of ice due to gravity, creates distinct U-shaped landforms and deposition material.
exposed upon glacial retreat.
moraine = material left behind from a moving glacier (dirt, boulders).
can transport material FAR from origin.
mass wasting
movement of soil/rock due to gravity
rapid - landslide, earthquake, intense rainfall/snowmelt
slowly - as a creep, evidence of freezing and thawing cycles
tectonic processes produce what landforms?
oceanic trenches, volcanoes, mountain ranges, fault lines.
recent tectonic activity results in a relatively YOUNG LITHOSPHERE (subduction and spreading)
plate tectonics of mars and Venus
many extinct volcanoes
no erosion (water based) processes
–> lithosphere is much older than Earth’s
no tectonics, lithosphere does’t move over upper mantle, allows magma accumulation (hotspots)
Mars ‘Valles Marineries’ and Venus ‘Devana Chasma’ are big linear valleys (like Earth’s rift valleys), indicate potential old plate boundaries
(linearity indicates a plate boundary rather than a river, which meanders)
Define liquefaction
shaking during an earthquake causes loose sand to loose its strength and behave like a liquid temporarily
Water is squeezed out and comes out of the surface, land reconsolidates at a lower level
define mega thrust earthquake
plates are locked and elastic potential energy is released suddenly in a massive earthquake event, possibly causing tsunamis
how are tsunamis caused in NZ?
Seafloor earthquakes cause the biggest tsunamis, but ONLY if FAULT MOVEMENT IS VERTICAL (reverse or normal) so that water is displaced
canyons (Kaikoura, Cook Strait) have high steep sides, so when sediments fall a large amount of GPE –> KE
Turbidity current displaces large amount of water
Undersea eruptions
turbidity currents / underwater landslides NZ
NZ surrounded by continental shelf, plunges to deep ocean floor
shelf has many CANYONS
sediment accumulates (rivers carry sediment to sea, coastal currents carry)
four types of weathering
Freezing/thawing cycles
Biological weathering (Eg. by tree roots)
exfoliation / onion skin – sun heat causes rock surface to heat / contract, peeling over time
Chemical – by slightly acidic environment etc
(MOVEMENT of particles is erosion.)
weathering / erosion of southern alps
rapid weathering+erosion results in sharp pointed peaks
westerly wind + orographic rainfall causes erosion
braided rivers NZ
carries large amounts of sediment from the Southern Alps to the sea
