Download Endogena och exogena landformer

Vulkaniska and Tektoniska
Landformer
Kap 14
och Berg&Jord
Geomorfologi
• Geomorfologi
– Den vetenskapliga studien av processer som
skapar landskapsformer
• Landformer
– Den ytliga fenomen av jorden
– Endogena (eng. initial) och exogena (eng:
sequential) processer/landformer
Endogena och exogena landformer
En sprickdal/gravsänka (rift valley) I närheten av Quilotoa, Ecuador
Vulkanisk Aktivitet
• Vulkaner
– Endogen landform
– Stratovolcanoes are cone shaped
– Shield Volcanoes are dome-shape.
Stratovulkaner
• Formed of layers of felsic
magma and tephra
• Occur along subduction plate
boundaries
• Magma is generally very
viscous and gassy.
• Violent explosions where
huge quantities of tephra are
ejected along with white-hot
gasses.
• Steep-sided volcanic cone
due to the gummy nature of
the magma.
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Calderas
Våldsamt vulkanisk eruption
Centrala delen av vulkanen blir förstort
Kollapse resulteras i en centralt depression: caldera
Stora mängder av gas och damm I atmosfären
Caldera av en stratovulkan i Alaska
Satellite image of Santorini's caldera,
formed around 1600 BC.
Mt St. Helens, innan och efter 18 maj 1980
Var finns stratovulkaner?
Stratovolcanoes are produced by the subduction of tectonic plates.
Skjöld Vulkaner
• Formed over a hot plume of mantle magma.
• Composed of mafic magma which is thin and
runny and flows easily.
• Characterized by gentle slopes and broadly
rounded domes.
Platt rörelse över en Hot Spot
Life Cycle of a Hotspot Volcano
Basaltiska Landformer
• Flood Basalts
– Huge plains covered with basalts
– Occur where a mantle plume lies beneath the continental
lithosphere.
Basaltiska Landformer
• Cinder cones
– Frothy basaltic magma is ejected under high pressure from a
narrow vent, producing tephra.
– Forms a small, circular hill with a central crater.
Marion Island, skjöldvulkan över en Hot Spot i södra havet, här med cinder kon
Global Volcanic Activity
Volcanic Eruptions: A Natural Hazard
• Release huge amounts of poisonous, incandescent gases that will
kill living beings.
• Ash, cinders and ejecta (tephra) bury objects in the area.
• Hot lava destroys almost anything in their path.
• Earthquakes
• Tsunamis - Seismic sea waves
• Lahars –
• mudflows associated with volcanic activity, melting ice and snow
Landformer av tektonisk aktivitet
Two forms of tectonic activity:
1. Compression takes place when tectonic
plates collide.
2. Extensional plate motion occurs along rifting
plates.
Fold Belts
4 typer av förkastning
Normal förkastning
• Result from
extensional crustal
movements.
• Vertical movement
of the two blocks
exposes a fault
scarp.
• Multiple normal
faults create horst
and graben.
Fault Block Mountains
Transcurrent Faults
• Also known as strike-slip faults.
• Horizontal movement with little or no scarp
produced.
• Usually occur along the boundary of two
tectonic plates.
• The San Andreas Fault is the most
famous.
Öst-afrikas ”rift valley”: början av kontinentalt spridning
Jordbävningar
• A motion of the ground surface, ranging
from a faint tremor to a wild motion
capable of shaking buildings apart.
• The center of an earthquake is the focus.
• The motion is caused by slippage of large
blocks of crust under extreme strain.
• Volcanic events may also cause
earthquakes.
Richter Scale
• Earthquakes are
measured by the
Richter Scale.
• Each whole number
increase is an energy
release some 32
times greater.
• The largest
earthquake observed
had a magnitude of
9.5 – Chile, 1960
Moment Scale
Global Earthquake Activity
• Red dots show earthquake centres originating between 0
and 100 km depths.
• Black dots show earthquakes of magnitude 8.0 or
greater during the past 80 years.
Seismic Sea Waves
• Tsunami are produced by a sudden movement
of the sea floor near the earthquake centre.
• Waves travel over the ocean with no discernible
height.
• Once the wave energy reaches the more
shallow water of the coastline, a large,
destructive wave, as high as 10 m is produced.
• Flooding from these waves has killed tens of
thousands of people.
• Japan, 1703 - 100,000 people died.