Unit 6 - Plate Techtonics & The Lithosphere

Geog 101

The oceanic crust is made out of

basalt (extrusive igneous=small crystals)

The continental crust is made out of

granite (intrusive igneous=large crystals)

The mantle is made out of

iron, magnesium, and silicon to nickel

Consistency of the mantle

relatively solid to plasticy

The inner core is made out

Solid iron and nickel

The outer core is made of

liquid iron

Oceanic crust is ____ than continental crust

More dense

Thickness in miles/kms for the crust

5-25 miles, 8-40 kms

Thickness in miles/kms for the mantle

1800 miles, 2900kms

Thickness of the liquid outer core and the solid inner core

2200 miles, 3500kms

Thickness of the crust to the solid inner core

6400kms and 4000 miles

What are minerals

Naturally occurring inorganic substances and are the building blocks for rocks

What are rocks

the aggregate of mineral particles and are based on formation

What are the 3 types of rocks

igneous, sedimentary, metamorphic

The rock cycle’s first few steps

Weathering, transportation, deposition, then turns into SEDIMENTS, lithification (Compaction and cementation), then turns into SEDIMENTARY ROCKS. All rocks that are formed go through uplift and exposure which leads to weathering.

The rock cycle’s steps after sedimentary rocks are formed

Metamorphism occurs, then turns into METAMORPHIC ROCKS, melting into magma, then crystalization leads to INTRUSIVE IGNEOUS ROCKS and consolidation leads to EXTRUSIVE IGNEOUS ROCKS.

What type of rock is volcanic

Extrusive igneous

What type of rock is plutonic

intrusive igneous

How are sedimentary rocks formed

compaction of sediments

How is metamorphic rock formed

Heat and pressure pushing towards heat

How is igneous rock formed

Formed when molten magma cools, solidifies, and crystalizes

How are intrusive rocks formed

cooling and solidifying beneath the surface (occurs more slowly because of surrounding pressure and insulation)

How are extrusive rocks formed

Cooling and solidifying upon breaking through the surface (occurs much faster because of contact with air or water)

What does rapid cooling look like

small pieces of rocks become tightly compacted

What does slow cooling look like

Bigger pieces further apart become compacted, but they are bigger pieces

Is cooling slower/faster and is crystalization larger or smaller in intrusive rocks

Slower, larger

Is cooling slower/faster and is crystalization larger or smaller in extrusive rocks

Faster, smaller

Intrusive rock examples

Course-grained granite

Extrusive rock examples

Fine-grained basalt and glassy obsidian

How is sedimentary rocks formed (more in depth answer)

External processes (weathering and erosion) help disintegrate rocks into sediments. Sediments are then transported via water, wind, ice, and or/gravity and deposited in basins where layers form (strata)

Sedimentary rock examples

Sandstone, limestone

How is metamorphic rock formed (more in-depth answer)

Rocks that have been drastically changed from heat and /or pressure. Usually, very different from pre-metamorphic state (harder, more compact)

Changes/ties that are identifiable

Shale to slate, granite to gneiss, limestone to marble

Who created the original idea of the origins of continents / Pangea

Alfred Wegener

Who was Vladimir Korp

He made the Koeppen system (climates)

How long ago was pangea

225 million years ago

How long ago was laurasia

135 million years ago

When did the dinosaurs go extinct?

65 million years ago

What did Pangea break into?

Gondwana and laurasia

How much do plate tectonics move per year

an inch

How many major plates are there?

7

How many intermediate plates are there?

7-8

How are they moved?

convection currents of magma from the upper mantle move them within the asthenosphere

What is the ring of fire?

Very intense area with frequent earthquakes and volcanoes

What is the lithosphere also known as?

The crust and upper mantle and the rockosphere

What is plate divergence?

Plates moving away from one another or rifting within a major plate

Examples of plate divergence

Mid-oceanic ridge / mid Atlantic ridge, east African rift, Lake Baikal

What is the process that happens at the mid-oceanic ridges

seafloor spreading

What area on earth is the most deepest and volumnous

Lake Baikal

What are grabens

depressions in land caused by faults

Example of a graben

The Niagara falls

What is seafloor spreading?

magma rises and pushes through the upper mantle, forcing the oceanic crust outward near continents on each side.

What are ocean ridges

Shallow parts of the ocean floor: rift and ridge and are sites of seafloor spreading (mid-ocean ridges)

What are trenches

Narrow belts of deep water (>6km) sites of subduction

Deepest trench

The mariana trench

Where do continental rift valleys develop

Where divergence takes place within a continent. As spreading proceeds, blocks of crust drop down, forming a rift valley.

Continental rift valley example

Lake Tanganyika

What is plate convergence?

Plates that collide

What plate subducts in a convergent boundary?

The denser plate (crust) subducts the lighter one

3 types of convergence

oceanic/continental, oceanic/oceanic, continental/continental

Oceanic-continental

The denser oceanic crust subducts continental crust upon contact, followed by oceanic crust sinking into the mantle.

What forms on land and in the subduction zone in oceanic/continental

Mountain ranges on land, oceanic trench forms in subduction zone

Example of oceanic/continental

Andes Mountains O

Oceanic-Oceanic

Older, denser plate will subduct younger one. Volcanoes often develop (island arcs)

Examples of oceanic-oceanic boundary

Aleutians of Alaska, Islands of Japan, Islands of Caribbean, lesser Antilles

What is found in the subduction zones of ocean-oceanic?

Large earthquakes

Continental-continental

Continental crust is too buoyant for much subduction, thus huge mountain ranges develop, volcanism is rare

Examples of continental/continental

Mt. Everest in the Himalayas

How did the Himalayas form?

India’s subcontinent collided with the Eurasian landmass/plate

Transform boundary

Two plates moving past one another laterally. Along great fractures called transform faults

Transform boundary example

San Andreas Fault

Mantle plumes

rise of magma to the surface in the interior regions of a plate. Often, the hotspot stays in place, but landforms move with the drifting plate.

What are mantle plumes

hot spots

Example of a hot spot

Yellowstone park

Terrane

Mass of lithosphere carried a long distance by a drifting plate. It eventually converges with another plate. (too buoyant for subduction, so it is rather fused (accreted) to the other plate. It is a key reason for continental expansion.

Where are volcanoes generally found

Mostly on plate boundaries

what percent of volcanoes is found in the ring of fire?

75%

How many actives volcanoes are there? where are they mostly located?

500, mostly underwater

What is pyroclastic material?

Fragmented material ‘shot out’ during eruptions. (rock fragments, lava, blobs, ash, dust)

The chemical structure of magma determines what?

The nature of the lava/pyroclastic material and the explosive capabilities of the volcanoes

Lava and ash flows can produce what?

Fertile soils

Many lava flows are not extruded from volcanoes, but what?

Fissures. Many fissures create floor basalts (accumulated lava layers)

Shield volcanoes

Not steep-sided. Hawaiian islands are composed of numerous shield volcanoes

What does basaltic lava (fluid and easy flowing) form? (Shield volcanoes)

usually forms low lying shield volcanoes

Composite/strato volcanoes tend to

erupt more violently.

Composite/strato volcano eruptions

alternate between lava-based lava-based, non violent eruptions and ash based, violent eruptions. Because of this, layers/strata are formed.

Composite/strato volcanoes are

generally very tall and steep sided

Lava/plug domes have

very viscous lava that doesn’t flow far.

Lava usually

bulges up from the vent and the dome will grow by expansion from below and within.

Lava/plug domes are generally

not very tall and irregularly shaped.

Shield volcano examples

Hawaiian islands, Tahiti

Composite (strato volcanoes) examples

Mt Fuji Japan, Mt. Rainier Washington, Mt. Shasta CA, Mt. Vesuvius Italy, Mt. St, Helens Washington.

Lava dome/ plug dome examples

Lassen Peak, CA, Mono Craters CA

Cinder cone examples

Paricutin Mexico, Sunset crater, Arizona

Cinder cones are

small and generally created by loose pyroclastic material

Caldera

On occasion, a volcano may expel so much material that the summit collapes into its emptied magma chamber. A crater then forms, usually surrounded by steep cliffs on all sides.

Caldera example

Crater lake, Oregon

Earthquakes

A shaking or trembling of the earth that is volcanic or tectonic in origin

3 Main techtonic causes

Considerable compression causes crust/rocks to fold. Considerable tension causes the crust/rocks to collapse. Plates moving laterally past one another can cause friction. Vibration signifies the release of energy caused by sudden movement.

Earthquake scale

Richter scale