1.1 Flashcards
What is the Lithosphere
The lithosphere is the crust and the top layer of the mantle (solid)
What is plate tectonic theory
Theory created by Alfred Wegener in 1912 he suggested that tectonic plates move
Why do plates move
1) mantle convection currents
2) slab pull
3) subduction zone movement
4) sea floor spreading
List the characteristics of the crust
- Up to 400 degrees
- Its solid
- It’s the layer we live on
List the characteristics of mantle
- Up to 870 degrees
- Less dense
- Upper part is solid. Lower part is semi-molten
List the characteristics of the outer core
- 4400 to 6100 degrees
- Dense
- Liquid iron and nickel
List characteristics of the inner core
- 7000 degrees
- Very dense
- Solid (radiates heat)
What are the processes at Divergent Processes
Sea floor spreading - rising magma
Large number of shallow focus earthquake
Plates moving apart from one another
What are the land forms found at divergent plate boundaries
Shield volcanoes
Rift valleys
Characteristics of Convergent plate boundaries
Plates move towards each other
One slides below the other (oceanic) - high magnitude earthquakes
This is called a subduction zone
What is a volcanic hotspot
Volcano that exists in the middle of a plate
What is a mantle plume
Long-lived areas of high levels of heat flow within the mantle
Give three examples of volcanic hotspot islands
- Hawaiian islands
- Galapagos islands
- Canary islands
How old is the Hawaii Emperor Sea Mount Chain
5.6 million years ago, to now
What is the major type of volcano found in Hawaii
Shield volcano - non eruptive
- gentle slope
- low viscosity - lava flows easily & quickly
- frequent eruptions
Explain the reasons for the shape of Hawaii’s volcanoes
Because the volcanoes are not explosive eruptions, the lava easily and gently flows out and hardens creating gentle slopes
Why does the hot spot stay in the same place
Magma finds weaknesses in the lithosphere and hardens on sea floor
Suggest why there is a sharpe bend in the Hawaiian Island chain
Plate movement changes
Intra-plate activity
Occurring within the middle of a plate
What does Viscosity mean
How sticky
What were the three different suggestions of Alfred Wegener - Pangea
He suggested:
•Biological
•Geological
•climatological
Biology evidence of Pangea
- Mesosaurus - small reptile. Fossils and remains found in South America & Africa
- A plant which existed when coal was being formed has been located in India and Antarctica
Geology evidence of Pangea
•Rocks f similar age, type, structure and formation found in South Africa and Brazil
Climatology evidence for Pangea
- Coal found under Antarctic ice cap
* Evidence of glaciation in Brazil and India
What is an Earthquake
Sudden shaking of the ground
Where do Earthquakes happen
Along plate boundaries
Why do Earthquakes happen
Release of friction/tension of the plates
Caused by sudden movements near the Earth’s surface along a fault
What is a fault
A fracture in the rocks that make up the Earth’s crust
What is the Epicenter
The point at the surface of the Earth directly above the focus
What is the Focus
The point within the Earth where an earthquake rupture starts
What are seismic waves
Waves that transmit the energy released by an earthquake
List the characteristics of P-Waves
‘P’ =pressure
- Travel fast
- First waves to arrive
- No one knows they’ve passed
- Send vibrations, push & pull weakening the rock
List the characteristics of S-Waves
‘S’ =Secondary
- Travel slow
- Pulling rock side to side
- People can feel this
- Cause damage
Like the characteristics of a Surface Wave (L-Wave)
- Large
- Move left and right , up and down
- Buildings fall
What factors can increase the severity of an earthquake
- Hospitals being built furthest away on cheap land
- Old buildings, weak - quality comes down to wealth (e.g) Nepal
- Buildings closest to river - geology type, softer rock, shakes for longer
What are the characteristics of a Shield Volcano
- Non eruptive
- Gentle slopes
- Low viscosity - lava flows easily and quickly
- Frequent eruptions
What are Primary effects of an Earthquake
- Ground shaking (which causes infrastructural damage)
* Crustal fracturing
What are Secondary effects of an Earthquake
- Liquefaction
- Landslides/Avalanches
- Tsunami
- Aftershocks
What is Liquefaction
When land shakes so much the solid particles start to act like a liquid
What are the 7 main factors which increase the severity of volcanic hazards
1) Viscosity of the magma - high viscosity = high explosivity
2) Plate margins - convergent margins are the most dangerous
3) Explosiveness
4) The material ejected
5) Distance to populated area
6) Frequency
7) Prediction
How is a volcanic eruption measured?
How is it measured?
•Volcano Explosivity Index
It is calculated using the ash cloud height and the volume of products ejected into the air
Characteristics of Composite volcano
- Steep sides
- Formed from very thick, viscous lava that doesn’t flow easily
- Lava builds up around the vent
- Explosive eruptions relating to viscosity of magma (gases can’t escape)
Characteristics of Shield volcano
- Gentle slopes, shield shape
- Low viscosity- lava flows easily and quickly
- Gentle, non-explosive eruptions
- Frequent eruptions (Hawaii)
Primary effects of a Volcano
- Pyroclastic Flow
- Lava Flows
- Tephra and Ash Cloud
- Gas eruptions
Secondary effects of a volcano
- Lahars
* Jokulhaups
What is a Pyroclastic Flows (Primary)
A dense, destructive mass of very hot ash, lava fragments and gassed ejected explosively from a volcano and typically flowing at a fast speed
What is a Lava Flow (Primary)
A mass of flowing or solidified lava
What is Tephra and Ash Fall (Primary)
All explosive volcanic eruptions generate tephra and produce ash
Fragments of rock is explosively ejected
What are Gas eruptions (Primary)
Gases that are released during volcanic eruptions
What are Lahars (Secondary)
Volcanic mudflow on the slopes of a volcano
What are Jokulhlaups (Secondary)
Glacier - typical of glacial outburst flood
Why do mudflows occur
When volcanic material mixes with rain and flows
Why do eruptions occur
When pressure forces magma from chamber to main vent crater blown off
What is formed when lava cools
New rock / land
Characteristics of a Tsunami
- Often low in height out at sea (below 300mm)
- Grow in height as they hit shallow water
- A series of waves
- First wave not necessarily the largest or most destructive
- Long wavelength can mean up to an hour between waves
