Oxygen level up

You are down in the valley now, between the Lickey Ridge and Beacon Hill. You can breath again – you have escaped from the Ordovician Period of geological time to the Carboniferous – check out what the oxygen levels are like now!  Does it look as though your chances of survival may be improving? When you are walking over rocks from a time period with an oxygen level higher than today, then your oxygen supply will start to be topped back up without any score penalty. If you are starting your walk here at the golf course (Task Site 3), be sure to look at the information and questions for Task Sites 1 and 2 before going any further.

The Carboniferous seems to have been a time of exceptionally high levels of atmospheric oxygen. One, perhaps the main, contributor to this was the enormous amount of plant growth at the time (e.g the great coal forming Carboniferous rain forests), which would have released large amounts of oxygen due to all the plant photosynthesis.

Plant life explosion

In the Carboniferous Period plant life really took off and for the first time there were forests, with really big trees and ferns.\n\nLots of oxygen was produced as the plants photosynthesised and this allowed the insects and reptiles to grow really big. Britain was in a humid tropical zone close to the equator with swamps and wetlands.

Big plate collision

Later in the Carboniferous, a big continental collision was happening, pushing up high mountains to the south of Britain, called the Variscan Mountains, and we became landlocked at the centre of the most massive continent that has ever existed on Earth, called Pangaea.

Climate much drier

The formation the massive Panagea continent caused the ocean circulation and the climate to change too, so that our part of the world became increasingly arid. It was at the time of this change that the rocks you are standing on now were laid down, with the land rising and the swamps of the great rain forests drying up.

There would have been a general elevation of the area due to the effect of the thrust of the Varisan Mountain building forces from the south.

Red soil

The soil gives a strong clue to the rock beneath. You can see it in mole hills or on the short, steep bank behind the tennis courts on your left as you walk up the path Beneath here is a red mudstone from the Carboniferous time. The mud which formed it was carried by streams and settled in a calm shallow lake – conditions like those shown in the previous picture. The muddy sediment washed off the land and carried in the Carboniferous streams had been weathered so that iron minerals in the sediment were oxidised, like rust. In this area the mud was carried by streams and rivers, like those shown in the previous picture, and settled in a calm shallow lake.

Red beds

Red coloured rocks are a strong indication of sediments laid down on the land as against under water.\n\nOn the drier conditions of the land iron combines with oxygen to form red minerals, often haematite. Under water iron forms dark green or black coloured minerals.

Task Site 3 Questions

How long ago were the rocks beneath you now laid down:

a) About 305 million years ago
b) About 525 million  million years ago
c) About 150 million years ago
d) About 250 million years ago

The rock is not exposed here, but look at the soil at the sides of the path and in any molehills. What colour is the rock beneath?

a) Dark grey
b) Green
c) Red-brown

If you pick up some of the soil you can press it into a shape, as it is full of clay. What does that suggest the rock type is here?

a) Limestone
b) Mudstone
c) Basalt

What causes the red colour of these rocks?

a) Iron oxide
b) Feldspar
c) Quartz
d) Biotite