Geology

Lanschaftsplanung BOKU

What are the three chemical layers of the earth?

Crust, mantle, core

Which is the largest chemical layer of the earth?

Mantle

What does the core of the Earth consist of?

iron, nickel, maybe oxygen

Which physical layer of the earth is broken into tectonic plates?

lithosphere

What are the seven major tectonic plates?

African, Antarctic, Eurasian, Indo-Australian, North American, Pacific, South American, Nazca

What are the five physical layers of the Earth?

lithosphere, asthenosphere, mesosphere, outer core, inner core

What are the two types of meteorites?

ferreous and stone

How did the earth form?

Solar fog, primitive Earth, differentiated Earth, developed Earth, modern Earth

Which layer is the only one that is liquid in the Earth?

outer core

Why is the inner core solid, despite the temperature being high enough to keep the minerals liquid?

Immense pressure

What is the most likely cause of the Earth’s magnetic field?

The circulation of molten iron and nickel in the outer core (convection current)

What are the three types of tectonic plate boundaries?

Convergent, divergent, transform

What two types of convergent boundary movements are there? (when two tectonic plates move toward each other)

subduction and collision

What is subduction?

When plates of different densities converge, the higher-density plate is pushed beneath the more buoyant plate, and descends into the mantle (forms a trench, melts into magma)

What’s typical for collision zones of tectonic plates?

Tall, non-volcanic mountains and a broad zone of frequent earthquakes

What are the two types of divergent boundaries?

continental rift zones and mid-ocean ridges

What is a hot spot?

An area in the litospheric plate where molton magma breaks through (creating mountains/volcanoes/islands)

Main differences between oceanic and continental plates?

Oceanic plates are much denser (because of more iron) and thinner

What are 3 direct and 4 indirect dangers of volcanoes?

1) damage to agricultural areas and infrastructure, 2) airfall (lava bombs etc.), 3) pyroclastic flow (most deadly), indirect: mud flows, avalanches, tsunamis, starvation (year without a summer)

What is pyroclastic cloud?

A fast-moving current of hot cas and volcanic matter (flattens buildings with kinetic energy, incinerates living organisms)

Five geochronologic time units

Eon, era, period, epoch, age

Oldest rock in Austria (name, age, location)?

Dobra Gneiss, 1,83 billion, Waldviertel

What is the epicenter of an earthquake?

The point on the surface that is directly above the hypocenter (place of first movement)

Two main types of earthquakes

Tectonic and volcanic (third type: collapse of structures)

What is a seismograph?

Instrument to record the motion of the ground, measures the magnitude of an earthquake (in numbers)

How do earthquakes cause direct damage?

Ground motion (destroying buildings), dislocation of surface topography (roads, railways, tunnels etc.)

What are indirect dangers of earthquakes?

Fire (gas lines, heaters etc. offset by movement), liquefaction (sediments with water turn to semi-quicksand), tsunamis, landslides

Where do the biggest earthquakes on earth occur?

Along the pacific plate, in areas of subduction and also on transform faults

Why does subduction cause earthquakes?

Downward movement of rigid lithosphere plate under another plate

What kind of mathematical scale is the richter scale?

logarithmic

What is the definition of the magnitude on the Richter scale?

the maximum height of the wave in the first seismic wave 100 km from the epicenter

What is orogeny?

Mountain building along a continental margin as the result of convergence

Sources of Earth’s internal heat?

leftover heat from when it was formed (primordial heat), fricitonal heating from denser core material sinking to the center and heat from the decay of radioactive elements

What is the current time period? In aeons, eras, periods and epochs

Phanerozoic, Cenozoic, Quaternary, Holocene

What is convection?

Heat transfer in a fluid, causes movement because the region closest to the heat source gets less dense and rises

What are the three main forms of heat transfer?

Conduction, convection, radiation

What is conduction?

Transferring heat via direct molecular collision (higher-speed particles collide with slower-speed particles, that then speed up)

What factors affect the density of seawater?

Salinity and temperature

How does salinity affect water?

Makes it denser

What’s the name of the malleable, flowing layer of the earth?

asthenosphere

What is the main rock type of the continental crust?

Granite

How does energy travel from the inner earth to the litosphere?

Convection

What is the oceanic crust mainly made of?

Basalt

What are Jupiter and Saturn made of?

hydrogen and helium

What do Uranus and Neptune consist of?

Hydrogen and helium, but also frozen compounds that make a solid surface

What do we call the epoch of the last ice age?

Pleistocene

4 regional capitals in Austria formed in the epoch of the Pleistoscene (ice age)

Bregenz, Innsbruck, Klagenfurt, Salzburg

What are the four eons that we can divide the history of the Earth in?

Hadean, Archean, Proterozoic, Phanerozoic

Which eon are we currently in?

Phanerozoic

How long is an eon?

At least 0,5 billion years

What three eras can the phanerozoic eon (our current one) be divided into? These are also the three eras since complex life evolved

Paleozoic, Mesozoic, Cenozoic

What is the current geological epoch?

Holocene (since 9700 BCE, after the last glacial period)

What era are we living in?

Cenozoic (started with the extinction event that ended the Mesozoic era)

What era is often called Age of the reptiles or Age of the Conifers?

Mesozoic era

What era is also called the Age of Mammals?

Cenozoic (current)

What geological period are we living in?

Quaternary

Three ways to classify rocks, depending on how they were formed

Sedimentary, metamorphic, igneous

How are sedimentary rocks formed?

From the compression of sediments that accumulate on the Earth’s surface (often have a disctinctive layering)

What are some common sedimentary rocks?

Sandstone, limestone

How are igneous rocks formed?

from Magma, that cools and forms rocks either under the surface or after a volcano eruption

What are some typical igneous rocks?

Granite, obsidian, basalt

How are metamorphic rocks formed?

Another type of rock is subjected to high heat and/or pressure, and is transformed (not melted) into a denser, more compact rock (new minerals form by rearranging or by reaction with fluids that enter)

What are some examples of metamorphic rocks?

Gneiss, marble, schist

What are the two types of igneous rocks?

intrusive (formed by cooling slowly under the surface of the earth) and extrusive (cooling quickly during an eruption)

What type of igneous rock is basalt?

extrusive

What type of igneous rock is granite?

intrusive

What kind of soil forms on top of limestone?

Rendzina

What kind of rock is limestone?

Sedimentary

What kind of soil forms on top of sandstone?

Podzol

What are the characteristics of podzol soils?

low level of moisture and nutrients (poor for agriculture)

What kind of soil forms on top of loess?

chernozem (very good agriculture soil)

What kind of soil forms on top of silicatic rocks such as gneiss or shale?

brown earth

What’s the average geothermal gradient in Germany?

3 degrees per 100 m

What 2 factors affect the sea level?

Internal fluctuations (changes in runoff from the land, melting, warmth expansion), land changes (uplift, sinking etc.)

What are the layers of the ocean?

Surface layer, thermocline and halocline (pycnocline is a function of these), deep ocean

What is the thermocline?

A zone of rapid temperature change in water (at least 1 degree per meter)

What is the halocline?

A zone where there is a rapid change in salinity in water

What is the pycnocline?

A zone where the water density increases rapidly with the depth (tends to coincide with the halocline and thermocline)

What kind of heat transfer happens inside the solid parts of the Earth (crust)?

Conduction

What plate boundary type is the most dangerous concerning earthquakes?

Convergent

What are areas of exchange between the lithosphere and the asthenosphere?

Mid Oceanic Ridges and subduction zones

How much to the major tectonic plates move per year?

Between 1,6 cm and 18 cm

What is the zone of the ocean called where there is a rapid change of dencity?

Pycnocline

What type of meteorite is most common?

stone (94 %)

Where are volcanoes typically found?

At diverging (MOR) or converging (pacific ring of fire) plate boundaries, usually underwater, as well as on hotspots

What are the three main types of magma?

basaltic, andesitic, rhyolitic

What are the darker areas of the moon?

Basalt (solid lava)

Differences between basalt and granite

Basalt is extrusive, 50 % quartz (vs 70 % in granite), high density, high crystallisation temperature, dark colour because of specific minerals

How is andesitic magma formed?

Melting ocean plate due to subduction (basalt, creates very gaseous magma)

How is rhyolitic magma formed?

By suduction of oceanic lithosphere under a continental plate (usually rich in water and has CO2)

How is basaltic magma formed?

Comes from the mantle, forms oceanic crust

What’s the longest mountain chain on the surface of the Earth?

The Mid Ocean Ridge

What’s the Mercalli scale?

Measures intensity of earthquakes based on observed effects, levels 1-10 (e.g. 2: felt only by few persons at rest, 10: masonry structures destroyed)

What is the magnitude vs intensity of an earthquake?

Magnitude is size of wave, intensity is felt effects

When did the Quaternary period start?

2,58 million years ago

When did the Holocene epoch start?

11,600 years ago (last glacial period)

When did the Cenozoic era start?

66 million years ago (with the cretaceous-paleogene extinction event)

What is the light-colored rock that makes up the crust of the moon?

Anorthosite (consists mainly of plagioclase feldspar)

What structures can silicates have?

single chain, double chain, isolated silicon tetrahedra, sheet, 3D/framework

Imagining the history of Earth as one year, what month did mammals evolve?

December