cecilia akselsson department of physical geography … · lund university, deparment of physical...

Lund University, Deparment of Physical Geography and Ecosystem Science

Minerals and rocksNGEA01, 2016

Cecilia Akselsson

Department of Physical Geography and Ecosystem Science

Lund University


Minerals and rocks

The rest of this week and end of next week + excursions

Weathering and soils for sustainable forestry

Photo: Jonas Åkerman

Photo: Cecilia Akselsson


Soils


First half of next week + excursions: Geomorphology

Glacial processesEsker: Dalarna, Sweden

Periglacial processesPolygon wedge ice:Svalbard

Erosion and eolian processesDunes: Namibia

Endogene processesVolcano, Mexico

Mass movements,fluvial processes,coastal processesBraided channel, New Zeeland

From Hess, 2013



From Hess, 2013

From Hess, 2013


wildfiresgreenhouse gases,aerosols

cloud formation

runoff

drainage

groundwater

weathering

nutrientuptake

litter

shortwaveradiation

longwaveradiation

greenhouse effecttemperature

evaporation

ecosystemservices

hydrosphere

biosphere

atmosphere

lithosphere

air pollutionCO2 emission

primary productiondecomposition

precipitationevapotranspiration

(Borrowed from B. Smith)

Geomorphology, minerals, rocks and soils:Important pieces in Physical Geography –

understanding the landscape


Understanding the landscapeExample 1: The building of a tunnel through “Hallandsåsen”

Feasibility and risk assessment


groundwater



• Started 1992

• 1997: Water leakage, tightening required, acrylamide leached, killed fishes, and affected cows

• Sydsvenskan 1 Nov 2008:

-The building delayed once again, tunnel will open in dec 2015

-Cost prognosis so far: > 10 billion SEK

-Reason: ”Unforeseeable rock conditions”

• First trains through the tunnel: december 2015

From Sydsvenskan 1 nov 2008


Movements along the Tornquist zone, mainly during the cretaceous and tertiary periods

From Hess, 2013




groundwater

Understanding the landscapeExample 2: When will the lake Gårdsjön recover from acidification?

When can we stop liming? 200 million SEK (20 million Euro)is spent on lake liming every year in Sweden!

(Photos: Cecilia Akselsson)


groundwater


When can we stop liming? 200 million SEK (20 million Euro)is spent on lake liming every year in Sweden!

(Data from IVL, www.ivl.se)

S dep. kg ha-1 y-1


groundwater


The answer can be found in the catchment!

http://info1.ma.slu.se/im/station/Gard.html

(Photo: Cecilia Akselsson)


How my research about sustainable forestryrelates to minerals, rocks, soils and geomorphology?

When will the lakes re-cover from acidification?

How much biomass can be harvested without depleting nutrients?

Will nitrogen leachto surface watersif we fertilize forests?

How will climate change affect?


Minerals and rocks

Soils

Today:



Photo: Cecilia AKselsson



Litterature - minerals and rocks

The first part of the chapter“Introduction to landform studies”

+ Handouts(compendium+exercise)

Slides will be put on homepage


The structure of the earth

(From Hess, 2013)


Elements, minerals and rocks

Elements – A pure chemical substance consisting of one type of atom distinguished by its atomic number

Minerals – Solid crystals formed by elements or compoundsof elements, with some specific properties…

Rocks – Consolidated combinationsof mineral material


(From Hess)


-Ca 100 elements

Elements – ca 100 naturally occurring (so far)


Elements – eight elements dominate in the crust


Minerals are solid crystals formed by elements or compounds of elements, with some specific properties…

-Solid

-Naturally found in nature

-Inorganic

-Specified chemical composition (limited variation)

-Atoms in a regular pattern → solid crystals

Minerals


Minerals – 4400 identified, seven categories

- Silicates

- Oxides

- Sulfides

- Sulfates

- Carbonates

- Halides

- Native elements

95% of all crustal rocks consists of < 20 minerals


Silicates

- Composed mainly of Si and O

- By far the largest mineral family

- Generally hard and durable

- Divided in:

-ferromagnesian silicates, “dark silicates”, examples: Pyroxene ((Mg,Fe)SiO3), Amphibole (Ca2(Fe,Mg)5Si8O22(OH)2)

-non-ferromagnesian silicates, “light silicates”, examples: feldspars ((Ca,Na,K)AlSi3O8),muscovite: KAl2AlSi3O10(OH)2

Quartz

Quarts (Bergkristall) Feldspar (fältspat) Muscovite(Photos:Jonas Åkerman)


Oxides

- Formed by an element combined with O

- The most widespread are the Fe-oxides

- Fe-oxides are often rock-forming, and a source of Fe ore

- Examples: Hematite (Fe2O3), Magnetite (Fe3O4)

(Photo: Jonas Åkerman)


Sulfides

- Formed by reduced S and one or more other elements

- The group contains many of the important ore minerals

- Common in many types of rocks, massive or in veins

- Examples: Pyrite, also called fool´s gold (FeS2),Galena/blyglans (PbS), Chalcopyrite/kopparkis(CuFeS2)

Pyrite

(From Hess, 2013)


Sulfates

- Formed by S, O and some other element

- Usually light-coloured

- Mostly found in sedimentary rocks

- Example: Gypsum (CaSO4 ∙ 2 H2O)


Gypsum


Carbonates

- Formed by C, O and one or more other elements

- Light-coloured or colourless

- Common consitutents of sedimentary rocks, e.g. limestone

- Examples: Calcite (CaCO3), Dolomite (CaMg(CO3)2)

Calcite



Halides

- The least widespread group

- Examples: Halite (NaCl), fluorite (CaF2)

Flourite

(Photos: Jonas Åkerman)


Native elements

- Minerals consisting of discrete elements

- Generally not rock forming

- Examples: Gold (Au), silver (Ag), platinum (Pt), copper (Cu), iron (Fe), sulphur (S)

Iron (Fe-meteorite)SulphurSilver

Platinum CopperGold(Photos:Jonas Åkerman)


Mineral properties

The physical properties of a mineral is determined by the atomic structure. The physical properties are:

-Crystal form (arrangement of atoms affects the shape)

-Color (results from interaction of light with the mineral)

-Specific gravity/density (mass per volume)

-Hardness (resistance to scratching)

-Luster (how mineral surfaces reflect light)

-Cleavage (the planes along which a mineral breaks)

-Streak colour (after scratching a non-glazed porcelain plate)


Mineral properties – Moh´s hardness scale


4. FLUORITE

2. GYPSUM

5.APATITE

1. TALC

7. QUARTZ

6. FELDSPAR

9. CORUNDUM

(Sapphire, ruby,)

8. TOPAS

3. CALCITE

Photos: Jonas Åkerman)


Mineral properties – Moh´s hardness scaleNumber 10: Diamond


Frequency of some minerals in Swedish soils

(www-markinfo.slu.se)


Examples of applications: 1. Mining


Examples of applications: 2. Soil fertility

(Photo: Cecilia Akselsson)


Examples of applications: 3. Groundwater quality

Good-quality groundwater

One of 16 environmental objectives in Sweden. Some harmful elements:U, Fl and Pb can occur naturally in some areas due to mineralogy


Rocks are consolidated combinations of mineralmaterial (one or, more commonly, several minerals)

Rocks

(From Hess, 2013)


1. Igneous rocks

-Plutonic (intrusive)-Volcanic (extrusive)

2. Sedimentary rocks

-Detritial (classic)-Chemical and organic

3. Metamorphic rocks

-Foliated-Non-foliated

Three types of rocks with different origin


Diorite


Gneiss

Sandstone

(From Hess, 2013)


Igneous rocks

Terms and definitions:

-Igneus = “fire”

-Magma: molten rock beneath the Earth surface

-Lava: molten rock floating or squeezed up on the surface

-Pyroclastics: tiny pieces of solid volcanic rock ejected outon the surface during a volcanic eruption. Can form rock.


Igneous rocks

Different ways to classify igneous rocks:

Based on composition:

-Felsic: Relatively large amounts of silica (SiO2).Light-colored with large amounts of qwartz and feldspar.

-Mafic: Relatively low amounts of SiO2. Dark-coloredwith large amounts of Mg- and Fe-rich silicates (e.g. olivineand pyroxene). Higher densities and melting points

Based on where they form (and texture):

-Volcanic/extrusive: Forms from cooling of lava or bonding of pyroclastics on above surface. Fine-graineddue to fast cooling.

-Plutonic/intrusive: Forms from cooling of magma belowsurface. Coarse-grained due to slow cooling.


Igneous rocks

(From Hess, 2013)


Sedimentary rocks

Sedimentory rocks are formed when deposited particles consolidate

(From Hess, 2013)


Sedimentary rocks

Compaction and cementation (infilling of pore spaces by e.g silica, carbonate and iron oxide)

(From Hess, 2013)


Sedimentary rock formation

Rock

Sediment

Deposits of sediments

Sedimentary rocks(often with stratification)

Weathering (mechanical and chemical)

Transport (water, wind, ice, gravity)

Consolidation through compactionand chemical cementation


Sedimentary rock in the Olympic mountains of Washington

(From Hess, 2013)


Three subcategories based on formation

-Detrital/clastic: Composed of fractions of preexisting rocks in the form of cobbles, gravel, sand, silt or clay. Examples: Shale/mudstone (44%), sandstone (32%), conglomerate.

-Chemical: Formed e.g. through precipitation of solids from ions in solution. Example: Limestone (22%).

-Organic: Composed of compacted remains of dead plant material. Example: lignite.

Sedimentary rocks

Sandstone

(From Hess, 2013)

(Photo: Jonas Åkerman


Metamorphic rocks

(From Hess, 2013)

Metamorphic rocks form when heat and/or pressureact on sedimentary or igneous rocks


Different types of metamorphism

- Contact metamorphism: Magma comes in contact with surrounding rocks, altering them through heat and pressure

- Regional metamorphism: Large volumes of rock deep down in the crust is subjected to heat and/or pressure for a long time, e.g. through lithospheric plate processes.

- Hydrothermal metamorphism: Hot, mineral-rich fluids flows through cracks in rocks


Metamorphic rocks – two types

- Foliated: Rocks where the minerals show a prominent orientation. Example: Gneiss.

- Nonfoliated: Rocks without foliation are formed fromrocks dominated by a single mineral. Examples: Sandstone forms qwartzite and limestone forms marble.


Gneiss


Bedrock…and mineral content in soil

(www-markinfo.slu.se)(based on SGU´sbedrock map)


The rock cycle

(From Hess, 2013)


Minerals and rocks

Soils

Tomorrow:



Photo: Cecilia AKselsson


cecilia akselsson department of physical geography … · lund university, deparment of physical...

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