Geological & Meteorological Activity (College Board AP Biology)

• Geological (rocks) and meteorological (weather related) events affect habitat change and ecosystem distribution
• These events are not necessarily anthropogenic - they would have happened anyway, without human impact
  • Although human activity may well have accelerated the rate at which such events have been occurring
• Some examples of geological and meteorological events that affect ecosystems:

El Niño

• An El Niño occurs when the sea temperatures are 0.5^oC above average
• This leads to warmer than average weather in the eastern Pacific, occurring every 2-7 years
• The temperature of the ocean off the coast of Peru rises an average of 6-8^oC causing thermal expansion and sea level rise
• Water off the coast of Australia and Indonesia is cooler and precipitation is reduced leading to droughts in Australia

Causes of El Niño 

• In a non El Niño year there is descending air over the eastern Pacific and rising warm moist air over the western Pacific 
• In an El Niño year the winds are reduced or reverse (going west to east) leading to a reversal of the conditions and rising air over the eastern Pacific and descending air over the western Pacific

Effects of El Niño

• Drought in some areas, affecting forest and wetland ecosystems
• Dying vegetation affects water drainage and acidification of the soil
• all of these changes create abiotic and biotic changes in ecosystems that can upset the balance of species within them

Continental Drift

• The science of plate tectonics puts forward a view that the main continents are always in motion
• This creates change in the distribution of important resources for life such as minerals
• Heat from the Earth's mantle is also distributed differently if there is a seismic event such as a volcano or earthquake
• All of this creates abiotic change that impacts ecosystems over the whole planet

The red dots show areas of high seismic risk; these are mainly at the edges of the tectonic plates and can cause dramatic abiotic change to ecosystems

Meteor Impact

• Whilst the majority of non man made events that have changed ecosystems are of terrestrial origin, some effects from outside Earth have been noticeable
• The best documented example is the asteroid impact which is believed to have ended the age of the dinosaurs
• A high concentration of the element iridium was found near to a known asteroid impact area called the Chicxulub crater, a crater formed around 66 million years ago off the coast of Mexico
• Iridium is extremely rare in other parts of Earth
• The fossil record shows this coincided with the mass extinction event that ended the dinosaurs' era
• The impact created clouds of hot dust and vapor that was lethal to most life forms
• The chemical composition of the soil, water and air after the impact was so different that in time, new species evolved and new ecosystems developed