Formation of the british isles

Question 1

name the 3 categories of sedimentary rockand give examples

Answer 1

Clastic- congolorate, sandstone, siltstone, mudstone; formed from pre existing rock witch have been transported
Chemical: evaporites, ironstone, limestone, - percipitated from water solution ie salt-halite
Biological: coal, chert, limestone- of biogenic, biochemical and organic origin

Question 2

Name and explain the 2 types of igneous rocks, give examples

Answer 2

Intrusive: Granite, Diorite, Gabbro, formed when magma cools within the crust
extrusive: Rhyolite, Andersite, Bassalt formed when magma solidifies on the earths surface

Question 3

Name the 2 types of metamorphic rocks

Answer 3

Foliated- Pressure (and mayby heat) Slate schist gneiss

Non-foliated- Marble, no pressure

Question 4

Magma.
Where is it formed?
Why does it move upwards?
What grows in magma as it cools?

Answer 4

• in the upper mantle, and crust where there is suficient heat to partially or fully melt rocks
• because it is less dense than solid rock
• solid crystals, dominantly silicate at first, then more crystals grow and become interlocked forming a hard crystaline rock

Question 5

Mid ocean ridges

• What kind of plate margin are they?
• what types of rock are formed here?

Answer 5

-constructive
-oceanic crust rock
+pillow bassalt
+ Gabbro
+ bassalt and gabbro are dark and heavy, because they contain lots of iorn and not much silica

Question 6

Island arc subductions

• what kind of plate margin are they?
• Why do these plate boundaries occur?
• what happens at these plate boundaries?
• What is the magma formed rich in and why?
• what kind of igneous rock does this form?
• What are the properties of this kind of magma?
• What type of erruption does this cause?

Answer 6

• Convergent
• Older crust is pushed away from MOR, creating convergent forces between the oceanic crust and new crust that it meets
• old oceanic crust (cols and dense) is forced below young oceanic crust (hot and buoyant) oceanic crust, the upper layer of the decending crust and th overlying mantle melt, water id releast from the melting minerals,
• Water and silicate minerals
• Andersite, lighter coloured and less dense as they contain less iorn/ magnesium
• Viscous
• Ash fall- pyroclastic flows, domes that explode violently

Question 7

Continental arc subduction

• What happens when island arcs are transported into continents?
• what happens eventually when all the oceanic crust has been subducted? aincient and modern example?
• what kind of rocks does it create and what are examples of these in the UK

Answer 7

• terranes are formed
• continental colision (orogeny) caledonian(siluria/devonian) variscan (Carboniferus/permian) - himalayas (now)
• creates granites i.e caledonian=scotland variscan=cornwall

Question 8

Metamorphic rocks
describe the level of pressure and tempreture in:
-seafloor +thisck sedimentary sequences
-subduction zones
-around igneous intrusions
-deep in continental crust

Answer 8

• low t+p
• low t high p
• high t low p
• high t high p

Question 9

Explain how the following metamorphic rocks are formed

• Bluschist
• slate schist gneiss
• Migmatite

Answer 9

-subduction of wet/ cool bastltic