Engineering geology lecture 1 Flashcards
What is the definition of a mineral?
Naturally ocuring inorganic substance which has a definite chemical composition and presents an ordered atomic arrangement
What is the definition of a rock?
An aggregate of one or more mineral, the nature and the properties of a rock are determined by the minerals in it and the manner in whcih the minerals are arranged relative to each other
What rock is chrystallised from molten magma?
Igneous
How are sedimentary rocks fromed?
From erosion on the Earth’s surface
How are metamorphic rocks formed?
They are altered by heat and/ or pressure
Which environment do Igneous rocks come from?
Underground, as lava flows
What rocks are formed in deposition basins, mainly sea?
Sedimentary
Where are metamorphic rocks found?
Mostly deep inside mountain chains
What type of rock is described as a mosaic of interlocking crystals?
Igenous and metamorphic
What is the texture of a sedimentary rock?
mostly granular and cemented
Wnat is the structure of an ingeous rock?
massive (structureless)
What is the structure of a sedimentary rock?
Layered, bedded, bedding planes present
What is the structure of a metamorphic rock?
Chrystal orientated
What type of rocks have uniform high strength?
Igneous
How strong are sedimentary rocks?
Variable low, planar weaknesses present
How strong are metamorphic rocks?
Highly variable
Can have planar weakness
What are some main types of Igneous rock?
Granite
Granodiorite
Basalt
What are some main types of Sedimentary rocks?
Sandstone
Limestone
Clay
What are some main types of metamorphic rocks?
Gneiss
Schist
Slate
What characteristics are helpful when dealing with minerals?
- Colour
- Lustre (appearance/ reflectance)
- Form (shape/ group/ clustering)
- Hardness (resistance to abrasion)
- cleavage (preferential split)
- Fracture (nature of broken surfaces - lack of cleavage)
- Tenacity (response upon sudden impact i.e. malleable vs brittle)
- specific gravity
What are the 2 different classifications of minerals?
- Silicate minerals
2. non - silicate minerals
What kind of mineral is olivine, and what colour is it?
Pale olive-green
Silicate mineral
What kind of mineral is pyroxene and what colour is it?
Dark colour (black) silicate
What kind of mineral is amphibole and what colour is it?
Dark colours (various) silicate
What kind of mineral is Mica?
Slicate
It is various colours
What kind of mineral is Feldspar and what colour is it?
Pink/ white/ colourless
Silicate
What kind of mineral and what colour is silica?
Colourless
silicate
What is the mean feature of the mica group?
Readily splits into thin flakes
Transparent in a single sheet
Why does the mica group split into thin flakes?
it has cleavage perfectly parallel to the basal plane
What are two common micas?
Muscovite (colourless/ silvery)
Biotite (dark brown to black)
What happens when mica weathers?
Metal ions are removed from the minerals
Results in soluble metal ions and clay minerals
What are 2 common Feldspars?
Alkali Feldspar (pink or white) Plagioclase feldspar (white, colourless or grey)
What reaction occurs when feldspar weathers?
Hydrolysis - a reaction between the minerals of water and the H+ and OH- ions present in water
Ksilica +(H+OH-) –> HSilicate + (K+OH-)
What is formed during the weathering of feldspar?
Kaolinite
Where do extrusive igeneos rocks come from?
erupting volcanoes
oozing fissures
How are extrusive igneous rocks formed?
When magma exits and cools above the Earth’s surface
Where do intrusive igneous rocks come from?
The Earth’s crust, only visible after the higher levels of rocks are eroded away
WHow are intrusive igneous rocks formed?
From molten rock insed the earth, cool at the earths crust
What is the range of silica content in igneous rock?
From 40-80%
How much silica does a felsic rock have?
high amounts
How much silica does a mafic rock have?
Low amounts
What are the 2 main types of Extrusive igneous rocks?
Fissure eruptions
Central eruptions
What are the characteristics of a fissure erupted igneous rock?
Low viscosity, far flowing basaltic lava
Produces fine-grained igneous rocks like plateau-basalt
What are the defining characteristics of a central eruption?
Ejection of lava, gases and broken rock
What is an example of a central erupted igneous rock?
Tuff - can be called a pyroclastic igneous rock
What texture does an intrusive igneous rock have?
Equigranular
What texture does and extrusive igneous rock have?
Aphantic texture
What word describes chrystal of all the same size?
Equigranular
What word describes crystals that are clearly larger than others?
inequigranular
What word describes large crystals surrounded by much smaller crystals?
Porphyritic
What facilitates the growth of larger and larger minerals?
The right temperature and pressure conditions for its continued growth
Which word describes a crystal with a regular shape?
Euhedral
What allows Euhedrals to form their natural shape?
They have had the space to grow
Anhedral minerals grow to fit in a space
Euhedral minerals form before Anhedral minerals
What temperature do olivine and quartz chrystallise at?
Olivine: 1200 C
Quartz: 700 C
How does susceptibility to chemical weathering relate to the melting point they chrystallise at?
The higher the chrystallisation temperature, the more suscpetible to chemical weathering
What kind of rocks are produced by the surface processes of the rock cycle?
Sedimentary
What are the 2 types of sedimentary rocks?
- Clastic “standard” (exogenic)
- Non-clastic “others” (endogenic)
What kind of sedimentary rocks have been deposited and either bedified or stratified horizontally?
Clastic
What are the very important conditions in which sedimentary rocks are formed?
Depositional environment
The available settlements
What sedimentary rock does mud turn into with pressure and temperature?
Shale
What sedimentary rocks does sand with pressure and temperature turn into?
Sandstone
What sedimentary rocks does gravel with pressure and temperature turn into?
Conglomerate
What is the definition of shale?
Rocks formed from compact muds, finely laminated structure with a tendency to break along parallel side fragments.
Mudstones typically break into blocky pieces
What is an example of a non-clastic sedimentary rock?
Limestone (carbonate rock)
Evaporties (salt rocks)
