Geohazards 3 (past climates and proof)

Carbon-Silicate cycle

Calcium carbonate in oceans used by marine organisms ends up in ocean sediments and are subducted into Earth's crust, eventually returned through volcanic venting.

Methane hydrates

Frozen deposits of methane gas found on the ocean floor and in ice cores

Red sandstones

Sand is oxidized, so UK was once a hot desert environment

Evaporites

Form in low rainfall high evaporation environments so UK must have been hot and dry

Tillites

Ancient boulder clay and glacial deposits, so UK was once a cold climate

Reef limestones

Mainly colonial corals, UK once found near equator

Cyclothem sequence

Deltaic sequence, forms coal due to rainforests in the UK

Smooth margin leaf species climate

Warmer climates

Jagged toothed margin leaf climates

Cooler climates

Relationship between stomata, temperature and CO2

Stomata density decreases when temperature and CO2 increase

CLAMP stands for

Climate-Leaf Analysis Multivariate Programme

Method for CLAMP

Decoding plant signals from overall appearance of leaves

Limitations of CLAMP

Must score features on a leaf subjectively

Leaf-margin analysis

Estimating average palaeo temperature by looking at the shape of leaves

Pros and cons of leaf-margin analysis

Easier than CLAMP but provides limited information

Leaf cuticle and stomatal density

Thickness of the cuticle indicates plant stress

Thin cuticle indicates

Lots of water in the environment so less stress of keeping water in

Wood indicates

Environmental changes through lifespan of the tree - development and maturation

Oxygen isotopes during glacial periods

O16 gets frozen in ocean sediments so the ratio increases

Oxygen isotopes during interglacial periods

O16 is evaporated out then returns as rain so the ratio is zero

Natural process adding CO2 to the atmosphere over time

Volcanic activity

Natural process removing CO2 from the atmosphere over time

The carbon silicate cycle

Snowball Earth

Hypothesis that proposes that the Earth was entirely covered by ice at points during the Earth's history