Luluhawa

Learning objectives

luluhawa

1 Apa itu

2 Bagaimana

terjadi

3 Jenis2 luluhawa4 Faktor2 yg mempengaruhi luluhawa

5 Impak/kesan

6 hasil

7 kepentingan

Luluhawa – suatu proses yang berlaku di permukaan bumi untuk memecah dan menguraikan batuan (break and decompose rocks) Enviromen: terhad kepada sejauh mana air tanah (groundwater) boleh menusuk masuk (penetrate) ke dalam permukaan bumi

luluhawa

Boleh dilihat sebagai destructive forces

- yang memecah, mengurai, mengubah bentuk dan keadaan fizikal dan kimia batuan

Boleh dilihat sebagai constructive forces – yang menghasilkan sedimen, membentuk batuan mendak, mineral, mendapan mineral, landform baru

Fakta asas luluhawa

Berlaku perlahan sepanjang masa Mengambil masa yang lama Semua jenis luluhawa berlaku kadang2

serentak dan tak terpisah satu sama lain. Dipisahkan untuk memudahkan pemahaman sahaja

Keadaan di keliling menentukan segalanya

Jenis2 luluhawa

1. Luluhawa fizikal

2. Luluhawa kimia

3. Luluhawa biologi

1. Luluhawa fizikal

Memecahkan batuan yang bersaiz besar kepada bahagian yang lebih kecilcontoh: wedging (pembajian), exfoliation (pengelupasan), thermal expansion (kembang haba), lelasan (abrasion), (wetting and drying (esp in shales), pressure release by erosion of overburden

Luluhawa fizikal

1 Frost wedging (pembajian ibun) – water expands when it freezes, breaking rocks into angular fragments; lazim berlaku dalam iklim temperat (ada ais)

Nota: apabila air menjadi ais, isipadu meningkat sebanyak 10% => mebungkah (pries) batuan

talus – terdapat di kaki bukit

Luluhawa fizikal

2 Exfoliation (pengelupasan) – bedrocks (batuan hampar) breaks into flat sheets along joints (kekar) which parallel the ground surface. This phenomenon is caused by expansion of rock when the pressure of overlying rock is removed by erosion => sometimes called unloading

Apa itu kekar?

Exfoliation Stone Mt

exfoliation

exfoliation

Active exfoliation Stone Mt

goblin

Mt Kinabalu

Mt Kinabalu

Mt Kinabalu

Luluhawa fizikal

3 Thermal expansion (kembang haba) – heat causes action; cooling causes contraction => expand and contract at different rate causes stresses along mineral boundaries. Repeated heating and cooling => batuan pecah

4 Lelasan (abrasion)

Batuan menjadi lebih kecil hasi drpd pergeseran dan pelanggaran semasa terangkut, contohnya di dasar sungai

Glasial, ombak dan angin juga boleh menjadi agen lelasan

Kelebihan kimia fizikal

Luluhawa fizikal memecahkan batuan ke saiz yg lebih kecil => menyediakan lebih banyak luas permukaan batuan bersaiz kecil untuk tindakbalas kimia berlaku

2. Luluhawa kimia

Memecahkan batuan secara kimia dgn menambah atau menanggalkan (removing) unsur2 kimia, mengubah unsur2 tersebut menjadi bahan2 baru

contoh: dissolution (pelarutan), hydrolysis (hidrolisis), oxidation (pengoksidaan)

Luluhawa kimia

1 Dissollution (pelarutan) – alters rocks by removing soluble minerals => soluble ions and insoluble ions => precipitate and crystallize (dalam tasik atau laut)

Ex: pembentukan garam, batu kapur, travertine

Batuan => ion larut/ tak larut => pemendakan

Luluhawa kimia

2 Hydrolisis – proses di mana feldspar are weathered to form clay

Note: clay make up half of sedimentary rocks on Earth

(Berapa jenis feldspar kita ada? Apakah komposisinya?)

Weathering of feldspar

Beberapa contoh t/b kimia

A. Solution of carbon dioxide in water to form acid

CO2 + H2O H2CO3 H+ + HCO3-

B. Solution of calcite

CaCO3 + CO2 + H2O Ca2+ + 2HCO3-

C. CaCO3 + H+ HCO3- Ca2+ +

2HCO3-

D. Chemical weathering of feldspar to form clay mineral

2KAlSi3O8 + 2H+ + 2HCO3- + H2O

K feldspar

Al2Si2O5(OH)4 + 2K+ + 2HCO3- + 4SiO2

clay mineral Silica in solution or as fine solid particles

2KAlSi3O8

Al2Si2O5(OH)4

K2OAl2O3

6SiO2

Al2O3

2SiO2

2H2O

Cara mengungkap formula untuk memudahkan kefahaman

Luluhawa kimia

3 oxidation – the process by which iron-bearing minerals (pyroxene, amphibole, biotite) weather to produce iron oxides

Di kawasan tropik iron bearing aluminosilicate => lateritic soils, red clayey soils

Oxidation reaction

4FeSiO3 + O2 +10H2O 4FeO.OH +

4H4SiO4

2Fe2SiO4 + 2O2 + 4H2O 4FeO.OH + 2H4SiO4

Fe pyroxene

Fe olivine

Goetite

3. Luluhawa biologi

Pemecahan batuan disebabkan oleh tindakan organisma hidup spt tumbuh2an, haiwan dalam tanah dan lichen (kulat? yang hidup di atas batuan dan kayu)

Hasil luluhawa

Weathering products

Average daily temperatures range from a minimum of 25o C to a maximum of 33o C.

has an average annual rainfall of more than 2500 mm

Malaysia

Hujan dan suhu

driest

wettest

Mineral stability in the weathering environment

Mineral didapati tak stabil dalam enviromen tertentu Minerals which formed at high temperature and pressures are least stable in the weathering environment and weather most quicklyMinerals which formed at lower temperatures and pressures are most stable under weathering conditions

Rates of weathering

Soil profile

D horizonFresh rocks

Soil profile

Eluviationilluviationleaching

Leaching/larutlesap: proses kimia yang menghasilkan unsur larut dan tak larut. Yang larut akan lesap ke bawah dalam profil tanah sementara yang tak larut akan terkumpul di bahagian atas profil tanah => warna membezakan lapisan tanah

Eluviation: removal of materials dissolved or suspended in water

Illuviation: horizon of maximum accumulation of suspended material or clay

Chelation: pembentukan kompleks kimia

Laterite profile

Acid run-off at gold mine

bryce

Oxidation effect

Oxidation effects

Staglatite-staglamite

sinkholes

Gred luluhawa (weathering grade), kekuatan ekapaksi dan rock-soil ratio

UCS(MPa) RSR

Gred VI tanah/soil

Gred V completely weathered <0.15 0-30

Gred IVhighly weathered 0.2-0.15 30-60

Gred III moderately weathered 0.4-0.2 60-90

Gred II slightly weathered 0.9-0.4 90-95

Gred I Fresh rock 95-100

Tengok transparensi lain

Sinkholes (tanah benam)

Bagaimana terjadi? Enviromental problem?

Jenis2 tanah

Residual soil - laterit, iklim tropik Transported soil – till, loess, iklim temperat

Tanih - pelbagai jenis tanah contoh: laterit, pedalfer, latosol,paleosol

Wentworth scale - grain size scale Particle name Particle diameter Gravel Boulders > 256 mm Cobbles 64 - 256 mm Pebbles 2 - 64 mm Granules 2 - 4 mm Sand Very coarse sand 1 - 2 mm Coarse sand 0.5 - 1 mm Medium sand 0.25 - 0.5 mm Fine sand 0.125 - 0.25 mm Very fine sand 0.0625 - 0.125 mm  Silt 1/256 - 1/16 mm

(or 0.004 - 0.0625 mm) Clay < 1/256 mm

(or < 0.004 mm) sesetengah buku guna takrif <2 mikron

Kitar batuan (Rock cycle)

Hakisan (erosion)

The movement of weathered material from the site of weathering. Primary agent is gravity, but gravity acts in concert with running water

pergerakan bahan terluluhawa dari tempat luluhawa berlaku ke tempat ia ditemui

Sedimentary cycle

Malaysia bagaimana?

Faktor yang mempengaruhi pembentukan tanah

1. Iklim (climate)2. Batuan induk (parent material)3. Relief (keadaan permukaan bumi)4. Vegetation (tumbuhan)5. Masa (time)

Sambung => batuan mendak

(lihat beberapa transparensi mengenai luluhawa)

Batuan mendak

apa

Bagaimana terjadi

Perubahan sebelum, semasa dan selepas pembentukan

jenis2

kepentingan

Apa kesudahannya?

Ciri2 utama Di mana

Sediment = loose particulate material (clay, sand, silt, gravel, etc.)

Sediment becomes sedimentary rock through lithification, which involves:

Compaction Cementation Recrystallization (of carbonate sediment)

Hasil drpd luluhawa ialah sedimen

Wentworth scale - grain size scale Particle name Particle diameter Gravel Boulders > 256 mm Cobbles 64 - 256 mm Pebbles 2 - 64 mm Granules 2 - 4 mm Sand Very coarse sand 1 - 2 mm Coarse sand 0.5 - 1 mm Medium sand 0.25 - 0.5 mm Fine sand 0.125 - 0.25 mm Very fine sand 0.0625 - 0.125 mm  Silt 1/256 - 1/16 mm

(or 0.004 - 0.0625 mm) Clay < 1/256 mm

(or < 0.004 mm) sesetengah buku guna takrif <2 mikron

Ternary diagram Sand-Silt-Clay

Kitar batuan (Rock cycle)

1 Terrigenous (detrital or clastic) – bumi/benua– Conglomerate or Breccia – Sandstone – Siltstone – Shale

2 Chemical/biochemical – Evaporites – Carbonate sedimentary rocks (limestones and dolostone) – Siliceous sedimentary rocks

3 Organic (coals) – Other - ironstones

Pengelasan batuan mendak

conglomerate

breccia

Quartz sandstone

Arkose (mengandungi banyak feldspar)

Greywacke (sand-sized rock fragments)

Silt: Grain size 1/256 to 1/16 mm (gritty) Siltstone

Clay: Grain size less than 1/256 mm (smooth) (< 2 micron)

Shale (if fissile) Claystone (if massive)

Note: Mud is technically a mixture of silt and clay. It forms a rock called mudstone (or mudshale if fissile).

shale

kaolin

B. Chemical/biochemical Sedimentary Rocks

This group includes the evaporites, the carbonates (limestones and dolostone), and the siliceous rocks. These rocks form within the depositional basin from chemical components dissolved in the seawater

Evaporites - The evaporites form from the evaporation of water (usually seawater).

Rock salt - composed of halite (NaCl). Rock gypsum - composed of gypsum

(CaSO4.2H20) Travertine - composed of calcium

carbonate (CaCO3), and therefore, also technically a carbonate rock; travertine forms in caves and around hot springs.

Bonneville Salt Flats of the Great Salt Lake, Utah. The lake bed is covered with rock salt which gives it the white color.

The salt is mined by the Morton Salt Company.

gypsum

Gypsum crystals, Marion lake, Australia

Carbonates - The carbonate sedimentary rocks are formed through both chemical and biochemical processes. They include the limestones (many types) and dolostones.

Two minerals are dominant in carbonate rocks: – Calcite (CaCO3) (batu kapur)-mudah berbuih

dgn asid lemah– Dolomite (CaMg(CO3)2) – perlu digores jadi

serbuk, baru bertindakbalas dgn asid

Carbonate rock names: Micrite (microcrystalline limestone) - very fine-

grained; may be light gray or tan to nearly black in color. Made of lime mud, which is also called calcilutite.

Oolitic limestone (look for the sand-sized oolites) Fossiliferous limestone (look for various types of

fossils in a limestone matrix) Coquina (fossil hash cemented together; may

resemble granola) Chalk (made of microscopic planktonic organisms

such as coccolithophores; fizzes readily in acid) Crystalline limestone Travertine (see evaporites) Others - intraclastic limestone, pelleted limestone

Stromatolitic limestone

Batuan karbonat di Mexico

Siliceous rocks - The siliceous rocks are those which are dominated by silica (SiO2). They commonly form from silica-secreting organisms such as diatoms, radiolarians, or some types of sponges. Chert is formed through chemical reactions of silica in solution replacing limestones.

Diatomite - looks like chalk, but does not fizz in acid. Made of microscopic planktonic organisms called diatoms. May also resemble kaolinite, but is much lower in density and more porous). Also referred to as Diatomaceous Earth.

Chert - Massive and hard, microcrystalline quartz. May be dark or light in color. Often replaces limestone. Does not fizz in acid.

. Organic Sedimentary Rocks (Coals) This group consists of rocks composed of organic

matter (mainly plant fragments). Because of this, they lack minerals (which must be inorganic, be definition). These are the coals. In order of increasing depth of burial (temperature and pressure):

Peat (porous mass of brownish plant fragments resembling peat moss)

Lignite (crumbly and black) Bituminous coal (dull to shiny and black; sooty;

layers may be visible) Anthracite coal (extremely shiny and black, may

have a slight golden shine; low density; not sooty; technically a metamorphic rock due to high temperatures and pressures to which it has been subjected)

others

There are several other interesting sedimentary rock types: Ironstones - Oolitic hematite, banded iron formations

Abundance of sedimentary rocks

Soalan

Maklumat apakah yang boleh dicerap dari pemerhatian batuan mendak?

Senaraikan…

Sedimentary structures form in the basin of deposition, as a result of the action of natural processes such as waves, currents, drying events, etc.

Beds or strata Cross-bedding Graded beds Ripple marks

-Current ripple marks (asymmetrical ripples) Oscillation or wave ripple marks (symmetrical ripples)

Mud cracks

Sedimentary Structures

Structures formed during deposition 1-4, after deposition 5,6

1 2 3

4 5 6

Ripple marks

Graded bedding, Jurassic of New Jersey

Graded bedding

kasar

halus

kasar

halus

mudcracks bagaimana terjadi?

ripples

rounding

sorting

High energy enviroment Low energy enviroment

varves

Cross stratification (berlaku semasa transgression-regression air laut)

Important note

Descriptive properties => interpretive properties

Geology => engineering Objective: to aid planning, design,

construction, mitigation, conservation, preservation

Sedimentary Environments Sedimentary environments are places where

sediments accumulate and sedimentary rocks form. They can be grouped into:

Terrestrial environments (non-marine) – Rivers (fluvial environment)/sungai) – Alluvial fans (kipas lanar)– Lakes (lacustrine environment)/tasik

- Swamps/paya- Deserts (aeolian environment) - Glacial environments

Transitional environments (at the transition between the marine and non-marine environments)

Beach and barrier islands Delta Lagoons Estuaries

Marine environments Continental shelf Continental slope and rise (deep sea

fans) Abyssal plain Reefs (karang)

Alluvial fan

Enviroment of sedimentary rx

SEDIMENTARY ENVIROMENTS

AGENTS & ENERGY

SOURCES

ALLUVIAL

WIND ACTION (Eolian)

Continental enviroment: fluvial

layering

beach

Model for landform development

Batuan mendak

Batuan hos kepada petroleum dan gas asli Mendapan mineral spt Cu, Pb, Zn, Tungsten dll

a bit about Si

14Si28.0855(3)The essentials

Name: silicon Symbol: Si Atomic number: 14 Atomic weight: 28.0855 (3) r CAS Registry ID: 7440-21-3 Group number: 14 Group name: (none) Period number: 3 Block: p-block Description     Here is a brief description of silicon. Standard state: solid at 298 K Colour: dark grey with a bluish tinge Classification: Semi-metallic

www.webelements.com

Silicon is present in the sun and stars and is a principal component of a class of meteorites known as aerolites. Silicon makes up 25.7% of the earth's crust by weight, and is the second most abundant element, exceeded only by oxygen. It is found largely as silicon oxides such as sand (silica), quartz, rock crystal, amethyst, agate, flint, jasper and opal. Silicon is found also in minerals such as asbestos, feldspar, clay and mica.Silicon is important in plant and animal life. Diatoms in both fresh and salt water extract silica from the water to use as a component of their cell walls. Silicon is an important ingredient in steel. Silicon carbide is one of the most important abrasives. Workers in environments where silicaceous dust is breathed may develop a serious lung disease known as silicosis.

Hydrolysis and condensation of substituted chlorosilanes can be used to produce a very great number of polymeric products, or silicones. These range from liquids to hard, glasslike solids with many useful properties.

Elemental silicon transmits more than 95% of all wavelengths of infrared and and has been used in lasers to produce coherent light at 456 nm.

Important facts

Isolation Here is a brief summary of the isolation of silicon. There is normally no need to make silicon in the

laboratory as it is readily available commercially. Silicon is readily available through the treatment of silica, SiO2, with pure graphite (as coke) in an electric furnace.

SiO2 + 2C Si + 2CO Under these conditions, silicon carbide, SiC, can form.

However, provided the amount of SiO2 is kept high, silicon carbide may be eliminated.

2SiC + SiO2 3Si + 2CO Very pure silicon can be made by the reaction of SiCl4

with hydrogen, followed by zone refining of the resultant silicon.

SiCl4 + 2H2 Si + 4HCl

Fakta penting mengenai Malaysia

Most cities and large towns in the Peninsula are located on a thin surface alluvium over limestone

and granite.

Malaysia is generally formed by highland, floodplain, and coastal zones (Figure 1.2 ). In the Peninsula, the Banjaran Titiwangsa from north to south divides the West Coast and East Coast states, while in Sarawak the Banjaran Kapuas Hula and Banjaran Iran border Indonesia. All of these ranges are governed by virgin forest

Malaysia is warm and humid throughout the year, as characterised by the equatorial climate, and has an average annual rainfall of more than 2500 mm with spatial variation shown in Figure  1 . 3 .

In the Peninsula wettest area is Taiping in Perak whilst the driest is Kuala Pilah in Negeri Sembilan (Figure  1 . 5 ).

 Average daily temperatures range from a minimum of 25o C to a maximum of 33o C. Relative humidity is high, sometimes exceeding 80%. Daytime cloudy hours are also high while haze lately is a frequent occurrence that will contribute to acid rains.  

Urbanisation poles are formed in many different ways including;

·          centrally in dense arrangements such as towns, cities, ports, commercial/business centres, and new development areas

·          linearly along road, highway, railway, river, estuary, and coastal areas

·          randomly located, including villages and high class residential areas

Next lecture

on metamorphic rocks