Geohazards and Georesources

volcanic hazards

lava flows, pyroclastic flows, lahar, tephra, debris avalanche, ash, gases, aerosols

measuring earthquakes - local

ML (local magnitude scale) which uses amplitude of ground shaking - doesn't differentiate between different waves so doesn't work well for deep, distant or large earthquakes

measuring earthquakes - large

MW (moment magnitude scale) which is a measure of the work an earthquake does in rocks sliding against eachother

earthquake alert systems

fast moving p waves arrive and are detected first so alerts sent out before s and surface waves arrive

tsunamis

caused by displacement of the sea floor. As waves move to shallower water, they become higher and more dangerous

landslides

affected by volcanic/earthquake activity, water, flooding, erosion, steepness of slope, rock type and grain shape, jointing and orientation of bedding planes, arrangement of rock layers, weathering processes, vegetation, human activity

coastal erosion

rock falls and cliffs receding

sinkholes

caused by soluble rocks such as limestones and evaporites

karst

landscapes caused by dissolution of soluble rocks. Forms underground sinkholes, cave systems, cenoles (pools), limestone pavements

coal formation

lots of plant activity in forests so normal decay processes can't keep up therefore plant matter buried as peat for billions of years

high grade coal

anthracite - very dark, good quality

coal age

most European/North American coal was formed by carboniferous coal swamps 300-325mya

anticlinal hydrocarbon trap

impermeable cap rock prevents rock oil moving up, creating gap for hydrocarbon

fault hydrocarbon trap

fault between impermeable rock causes empty space to be filled with hydrocarbon (rock oil)

fracking

mixture of water, chemicals and sand injected at high pressure to gas rich shale causing natural gas to flow to surface through fissures

geothermal energy from coal mines

warm water stored naturally in abandoned mines provides low carbon heating for homes

weathering

chemical alteration and mechanical breakdown of rock

physical weathering

weathering linked to exploitation and weathering of rocks

joints

weaknesses in rock due to tectonic processes or cooling and contraction

salt action (haloclasty)

salt crystals expand and grow inbetween gaps in rock grains. This can cause honeycomb weathering

granular disintergration

coarse rock breaks down grain by grain into fine particles, caused by differential expansion of minerals

frost wedging

water in crevices freezes and expands ~9% in volume. This cycle opens up more rock for water to get in

biological physical weathering

root systems track along rocks and push them apart. Water can now get in causing physical weathering

plant weathering

root exploration of cracks, water retention from surface moss

biological weathering

organic acid excretion from roots, uptake of selected ions causes increased solubility of rocks, decay of organic matter release organic acids and decay products, grazers distub rock's surface

chemical weathering

hydrolysis e.g. acid dissolving and leaching out the rock, acid dissolution from slightly acidic rainfall, oxidation of ions, chelation of polyvalent materials from organic/inorganic ligands

most susceptible minerals to weathering

olivine, pyroxene and amphibole

least susceptible minerals to weathering

k-feldspar, muscovite, quartz, biotite

chemical weathering and climate

tropics are hot and have high rainfall therefore lots of weathering

igenous rocks as soil parent materials

silica rich rocks produce acidic soils, silica poor rocks produce basic soils. ultrabasic soild from basalt have high amounds of Mg, Fe, Ni, Cr therefore limited plant life

zonal soils

well developed, reflect regional climate

azonal soild

immature, poorly developed soils

intrusive igneous rock soils

most acidic - granite: quartz, zonal soil. diorite: no quartz, feldspar. gabbro: fairly selective flora. ultrabasic - perioditie: highly selective, endemic flora

extrusive igneous rock soils

most acidic - rhyolite: azonal, poor plant cover. andesite: zonal soild, good plant cover and diverse flora. most basic - basalt: zonal soil, high diveristy

sedimentaty rocks as soil parent material

sandstone: rich in quartz, acidic, free and draining soild. shale: less acidic and less free draining. limestone: alkaline upon weathering, missing key elements.minerals therefore selective plants

peak district soil types

dark peak: north peak district, shale/gritstone surface rock. Acidic moorland dominated by heather and other species. white peak: south peak district, limestone surface rock. Alkaline grasslands with a rich diveristy of calcicole species. Soils lack nutriends therefore the area needs lots of different plant species

specialist flora and soil types

metallophytes are abundant in harsh environments of heavy metal-rich soil. e.g. peak district lead mines indicated by lead wort. can be used as prospecting tools for metal reserves

phytoremedication

using plants to remove contaminents such as heavy metals from soils