At the turn of the twentieth century, a teenager in Østerbro, Denmark felt the ground move beneath her feet. It was her first earthquake, but it wouldn’t be her last. More than two decades of study and observation later, Inge Lehmann’s work sent shockwaves through the scientific community. By observing earthquakes, she discovered the earth has both inner and outer cores. Her work has withstood the test of time. In fact, it’s still the foundation for seismological science today.
Inge used deduction and evidence to discover something unseeable. Today’s Doodle sheds light on her powerful but invisible discovery. Doodler Kevin Laughlin helps us experience the gift Inge illuminated for the world by revealing it as a glowing orb. Not all of his early drafts looked the same, but the earth’s inner core glowed at the center of each.
Pioneers like Inge Lehmann make this world a better place by helping us understand it from the inside out. But Lehmann’s legacy isn’t just scientific. Having been educated at a very young age in a Copenhagen school that treated female and male students as absolute equals, she was a strong proponent of gender equality. Her pioneering spirit is an inspiration to us.
– From Google, in honor of May 13, 2015, Inge Lehmann’s 127th Birthday
Mantle convection inside the Earth
Mantle convection is the very slow motion of Earth’s solid silicate mantle. It is caused by convection currents carrying heat from the interior of the Earth up to the surface.
The Earth’s surface lithosphere is divided into a number of plates. These are continuously being created and consumed at their opposite plate boundaries. Accretion occurs as mantle is added to the growing edges of a plate, associated with seafloor spreading. This hot added material cools down by conduction and convection of heat.
At the consumption edges of the plate, the material has thermally contracted to become dense, and it sinks under its own weight in the process of subduction usually at an ocean trench.
This subducted material sinks through the Earth’s interior.
The subducted oceanic crust triggers volcanism.
It is because the mantle can convect that the tectonic plates are able to move around the Earth’s surface.
Animation of mantle plumes within the Earth