At http://phys.org/print384004404.html … earth's magnetic field deflects solar radiation and allows life to thrive (or that is the theory). It is also supposed the core is made of iron and this generates the magnetic field. The argument in the past has been when in the history of the Earth the magnetic field began, the overriding mainstream view being that it was not terribly old (far from four billion years ago). The authors of the article in Nature have been doing some interesting and complicated research that cannot be criticised for its science integrity nor the way the experiment was conducted. They found that the outer core (liquid iron rather than the solid iron of the inner core) has the geodynamics to generate the field. The assumption is that the core is made of iron – but nobody can actually have a look so that view will rule the roost for the time being. See also www.nature.com/articles/doi:10.1038/nature18009 – and the same story is at https://wattsupwiththat.com/2016/06/02/ironing-out-the-mystery-of-earths… … where we have several pages of comments, supportive and sceptical.
See also www.livescience.com/39780-magnetic-field-pushes-earth-core.html … in which it claims the inner core rotates in the opposite direction to the outer core. The Earth's magnetic field is created by convection of hot liquid metal within the outer core which is the assumption made at the first link.
For those really into this go to www.esa.int/Our_Activities/Observing_the_Earth/Swarm/Earth_s_magnetic_he… … which should keep you busy for a while