<![CDATA[Happy birthday to Danish #seismologist Inge Lehmann (1888 – 1993) who demonstrated that the Earth’s core is not a single molten sphere, but contained an inner solid core, in ‘36.]]>Happy birthday to Danish Inge Lehmann (1888 – 1993) who demonstrated that the Earth’s core is not a single molten sphere, but contained an inner solid core, in ‘36. She was a pioneer , a brilliant seismologist & lived to be 105.⁠
⁠
As she first postulated, the earth has roughly 3 equal concentric sections: mantle, liquid outer core & solid inner core. 🧵

https://minouette.etsy.com/listing/72525124

]]>https://forum.fedi.dk/topic/ffdc3707-5161-4718-ac3d-11a79e87663a/happy-birthday-to-danish-seismologist-inge-lehmann-1888-1993-who-demonstrated-that-the-earth-s-core-is-not-a-single-molten-sphere-but-contained-an-inner-solid-core-in-36.RSS for NodeSun, 31 May 2026 19:56:45 GMTWed, 13 May 2026 11:55:49 GMT60<![CDATA[Reply to Happy birthday to Danish #seismologist Inge Lehmann (1888 – 1993) who demonstrated that the Earth’s core is not a single molten sphere, but contained an inner solid core, in ‘36. on Wed, 13 May 2026 20:04:42 GMT]]>@minouette Ele, these prints are simply awesome - great choice of subjects, fantastic image composition and brilliant technique. I look forward to seeing them in the thread!

]]>https://forum.fedi.dk/post/https://social.vivaldi.net/ap/users/116256575994654827/statuses/116569058991410866https://forum.fedi.dk/post/https://social.vivaldi.net/ap/users/116256575994654827/statuses/116569058991410866Wed, 13 May 2026 20:04:42 GMT<![CDATA[Reply to Happy birthday to Danish #seismologist Inge Lehmann (1888 – 1993) who demonstrated that the Earth’s core is not a single molten sphere, but contained an inner solid core, in ‘36. on Wed, 13 May 2026 18:03:23 GMT]]>@minouette “The only way to probe deep into the core is to employ massive earthquakes” has serious James-Bond-villain energy 😄

]]>https://forum.fedi.dk/post/https://ottawa.place/users/MichaelPorter/statuses/116568581939256065https://forum.fedi.dk/post/https://ottawa.place/users/MichaelPorter/statuses/116568581939256065Wed, 13 May 2026 18:03:23 GMT<![CDATA[Reply to Happy birthday to Danish #seismologist Inge Lehmann (1888 – 1993) who demonstrated that the Earth’s core is not a single molten sphere, but contained an inner solid core, in ‘36. on Wed, 13 May 2026 15:14:15 GMT]]>@hyc @minouette From Wikipedia. Temperature is about 5000 C or 10000 F.

The inner core is solid at high temperature because of its high pressure, in accordance with the Simon-Glatzel equation.[6]

]]>https://forum.fedi.dk/post/https://sigmoid.social/users/drgroftehauge/statuses/116567916926249653https://forum.fedi.dk/post/https://sigmoid.social/users/drgroftehauge/statuses/116567916926249653Wed, 13 May 2026 15:14:15 GMT<![CDATA[Reply to Happy birthday to Danish #seismologist Inge Lehmann (1888 – 1993) who demonstrated that the Earth’s core is not a single molten sphere, but contained an inner solid core, in ‘36. on Wed, 13 May 2026 13:09:13 GMT]]>@minouette out of curiosity, why isn't the inner core also molten liquid? Is it cooler than the liquid core?

]]>https://forum.fedi.dk/post/https://mastodon.social/users/hyc/statuses/116567425279795558https://forum.fedi.dk/post/https://mastodon.social/users/hyc/statuses/116567425279795558Wed, 13 May 2026 13:09:13 GMT<![CDATA[Reply to Happy birthday to Danish #seismologist Inge Lehmann (1888 – 1993) who demonstrated that the Earth’s core is not a single molten sphere, but contained an inner solid core, in ‘36. on Wed, 13 May 2026 11:58:48 GMT]]>She later also discovered the Lehmann discontinuity in the mantle. When she received the Bowie medal in ‘71 (1st woman to receive the highest honour of the AGU), her citation noted that the “Lehmann discontinuity was discovered through exacting scrutiny of seismic records by a master of a black art for which no amount of computerization is likely to be a complete substitute...”.⁠ 🧵5/5

]]>https://forum.fedi.dk/post/https://spore.social/users/minouette/statuses/116567148375776888https://forum.fedi.dk/post/https://spore.social/users/minouette/statuses/116567148375776888Wed, 13 May 2026 11:58:48 GMT<![CDATA[Reply to Happy birthday to Danish #seismologist Inge Lehmann (1888 – 1993) who demonstrated that the Earth’s core is not a single molten sphere, but contained an inner solid core, in ‘36. on Wed, 13 May 2026 11:58:35 GMT]]>That means, the p-waves from an earthquake can be recorded at seismic stations out to 105° from an epicentre & there is a zone which is in the core’s shadow. Lehmann found that there were some late-arriving P-waves are much larger angles (142 to 180°) which had been vaguely labelled ‘diffractions’. She showed that these could be explained instead by deflections of the waves which travelled through the outer core at her postulated inner core boundary.⁠
⁠🧵4/

]]>https://forum.fedi.dk/post/https://spore.social/users/minouette/statuses/116567147527894145https://forum.fedi.dk/post/https://spore.social/users/minouette/statuses/116567147527894145Wed, 13 May 2026 11:58:35 GMT<![CDATA[Reply to Happy birthday to Danish #seismologist Inge Lehmann (1888 – 1993) who demonstrated that the Earth’s core is not a single molten sphere, but contained an inner solid core, in ‘36. on Wed, 13 May 2026 11:58:18 GMT]]>through different media, these seismic waves can bend, reflect or be transmitted at any boundary. The difference in physical properties between the mantle & outer core causes a P-wave shadow. (For S-waves, the shadow zone is absolute because liquids, like outer core, do not support shear - imagine trying to cut water with a pair of shears and you can see this for yourself. Thus, no shear waves can make it through the outer core, & thus we can be certain the outer core is fluid). 🧵3/

]]>https://forum.fedi.dk/post/https://spore.social/users/minouette/statuses/116567146425006272https://forum.fedi.dk/post/https://spore.social/users/minouette/statuses/116567146425006272Wed, 13 May 2026 11:58:18 GMT<![CDATA[Reply to Happy birthday to Danish #seismologist Inge Lehmann (1888 – 1993) who demonstrated that the Earth’s core is not a single molten sphere, but contained an inner solid core, in ‘36. on Wed, 13 May 2026 11:57:58 GMT]]>The crust, on which we live is merely a thin scum on top of this slowly boiling pot. The only way to probe deep into the core is to employ massive earthquakes. There are 2 main types of seismic waves used: Primary (or P, or compressional) & Secondary (or S, or shear). Imagine a glass of water with a straw; the straw will appear broken at the air-water interface, because light bends as it enters the water. Just like light travelling 🧵2/

]]>https://forum.fedi.dk/post/https://spore.social/users/minouette/statuses/116567145107612414https://forum.fedi.dk/post/https://spore.social/users/minouette/statuses/116567145107612414Wed, 13 May 2026 11:57:58 GMT