Rocks And Their Formation

Question 1

How are sedimentary rocks formed?

Answer 1

Rock made by compression of layers of sediment over a very long time period.

1) Sedimentary rocks are formed from layers of sediment laid down in lakes or seas
2) Over millions of years the layers get buried under more layers and the weight pressing down squeezes out the water
3) Fluids flowing through the pores deposit natural mineral cement.

Question 2

What are examples of sedimentary rocks?

Answer 2

Chalk and limestone

They are mostly calcium carbonate and can be formed from sea shells.

Question 3

What do sedimentary rocks contain?

Answer 3

May contain fossils

Are susceptible to erosion

Question 4

How are metamorphic rocks formed?

Answer 4

1) By the action of heat and pressure on sedimentary (even igneous) rocks over a long period of time.
2) The mineral structure and texture may have changed, but the chemical composition is often the same as the original rock.
3) So long as the rocks don’t actually melt they’re classed as metamorphic. If they melt and turn to magma, they’re gone.

Question 5

Describe marble as an example of metamorphic rock.

Answer 5

Marble is formed from limestone or chalk. Very high temperatures break down the limestone and it reforms as small crystals. This gives marble a more even texture and makes it much harder.

Question 6

What exists in the earths crust?

Answer 6

Limestone, chalk and marble

They are all natural forms of calcium carbonate.

Question 7

How are igneous rocks formed?

Answer 7

Rock formed when magma cools and solidifies
It contains crystals that interlock
Size of crystals depends on the rate which the lava or magma cools
Slow= big crystals (granite)
Big= small crystals (basalt)