Mains Paper 1: Geography | Changes in critical geographical features
From the UPSC perspective, the following things are important:
Prelims level: World Magnetic Model
Mains level: Magnetic Pole Drifting
- Rapid shifts in the Earth’s north magnetic pole are forcing researchers to make an early update to a model that helps navigation by ships, planes and submarines in the Arctic.
Shifting Magnetic North Pole
- Magnetic North Pole wanders, and every few hundred thousand years, the polarity flips so that a compass would point south instead of north.
- Liquid churning in Earth’s core generates most of the magnetic field, which varies over time as the deep flows change.
- However, the magnetic field has been changing so quickly and erratically that while conducting a routine check in early 2018, British and US researchers realized drastic steps were needed.
- The shift they observed was so large it was on the verge of exceeding the acceptable limit for navigation errors.
- Scientists must periodically update the World Magnetic Model to map this process, and the most recent version – produced in 2015 – was intended to last until 2020.
Tracking the movement
- The wandering pole is driven by unpredictable changes in liquid iron deep inside the Earth.
- It’s moving at about 50 km (30 miles) a year.
- It didn’t move much between 1900 and 1980 but it’s really accelerated in the past 40 years.
- On the contrary, the South magnetic pole drift is very slow (less than 10 km per year).
- It has not changed much over the past few decades, and hence provided a much smaller contribution to the overall model declination error.
- The Earth’s magnetic field is in a permanent state of change.
- Magnetic north drifts around and every few hundred thousand years the polarity flips so a compass would point south instead of north.
- The strength of the magnetic field also constantly changes and currently it is showing signs of significant weakening.
Effect on Life
- Life has existed on the Earth for billions of years, during which there have been many reversals.
- There is no obvious correlation between animal extinctions and those reversals. Likewise, reversal patterns do not have any correlation with human development and evolution.
- It appears that some animals, such as whales and some birds use Earth’s magnetic field for migration and direction finding.
- Since geomagnetic reversal takes a number of thousands of years, they could well adapt to the changing magnetic environment or develop different methods of navigation.
Effect on Climate
- Earth’s magnetic field, which has existed for at least 3.45 billion years, provides a shield from the direct impact of solar radiation.
- Even with Earth’s strong magnetic field today, we’re still susceptible to solar storms that can damage our electricity-based society.
- The fluctuations in the number of cosmic rays hitting the atmosphere directly alter the amount of cloud covering the planet.
World Magnetic Model
- The World Magnetic Model (WMM) is a large spatial-scale representation of the Earth’s magnetic field.
- It consists of a degree and order 12 spherical harmonic expansion of the magnetic potential of the geomagnetic main field generated in the Earth’s core.
- The charts are used to convert between compass measurements of magnetic north and true north.
- It can be found in the navigation systems of ships and airplanes as well as geological applications (such as drilling and mining).
- Researchers from the U.S.’s National Oceanic and Atmospheric Administration (NOAA) maintain the WMM.
- The charts, known as the World Magnetic Model (WMM), are used to convert between compass measurements of magnetic north and true north
- The WMM is also part of map applications in smartphones, including the Google Maps App.