How do magnetic reversals affect migrating animals like sea turtles and birds?
Question: How do magnetic reversals affect migrating animals like sea turtles and birds?
Answer: No one knows, exactly, but whatever happens during geomagnetic reversals, the migrating species manage to survive. For instance, we have sea turtles that swim thousands of kilometers to mid-ocean islands that were once, millions of years ago, closer to the continents. Many reversals have occurred during that time, yet the turtles are still here.
Reversals take a long time to occur, many centuries, and presumably the migrators adapt as things slowly change. These animals rely on more than one set of cues to get where they're going?stars, polarized skylight, water chemistry, landmarks etc. So magnetic sensitivity is just a backup system of navigation, or one component of a more sophisticated way to stay on course. For instance, homing pigeons may be confused by solar storms that disrupt the geomagnetic field, but only during cloudy weather or other situations when all they can use is their magnetic sense.
Another factor to consider is that there's more than one geomagnetic field. The major portion, the dipole field, is the part that reverses, but there is a relatively minor component, the nondipole field, that persists. So while the main field may disappear in the middle of a polarity flip, some magnetic field remains at all times: A compass will always point somewhere. That's enough for navigation.
Magnetic reversals are a deep puzzle in geophysics.
Only recently have our computer models been able to generate them; some actual examples were used in the movie The Core.
Answer: No one knows, exactly, but whatever happens during geomagnetic reversals, the migrating species manage to survive. For instance, we have sea turtles that swim thousands of kilometers to mid-ocean islands that were once, millions of years ago, closer to the continents. Many reversals have occurred during that time, yet the turtles are still here.
Reversals take a long time to occur, many centuries, and presumably the migrators adapt as things slowly change. These animals rely on more than one set of cues to get where they're going?stars, polarized skylight, water chemistry, landmarks etc. So magnetic sensitivity is just a backup system of navigation, or one component of a more sophisticated way to stay on course. For instance, homing pigeons may be confused by solar storms that disrupt the geomagnetic field, but only during cloudy weather or other situations when all they can use is their magnetic sense.
Another factor to consider is that there's more than one geomagnetic field. The major portion, the dipole field, is the part that reverses, but there is a relatively minor component, the nondipole field, that persists. So while the main field may disappear in the middle of a polarity flip, some magnetic field remains at all times: A compass will always point somewhere. That's enough for navigation.
Magnetic reversals are a deep puzzle in geophysics.
Only recently have our computer models been able to generate them; some actual examples were used in the movie The Core.