The Hudson Bay Lithospheric Experiment

Geologists can usually interpret the rocks they encounter on Earth in the light of tectonic and volcanic processes presently operating at the plate boundaries. This approach works well for relatively young rocks (Phanerozoic: younger than 550 million years old), but for the older rocks that formed during Precambrian times (more than 550 million years old), the “plate tectonic” assumption must ultimately break down. Processes operating on the younger, hotter Earth would have been quite different to those we see today. Gathering detailed evidence preserved deep within the plates in the ancient cores of the continents (“shields”), is thus essential to our understanding of the early Earth. This can be achieved using data from dense seismograph networks, but building and maintaining them in remote areas is both logistically and financially challenging; innovative station and equipment designs are required to deliver the success enjoyed in gentler climes. The Hudson Bay Lithospheric Experiment (HuBLE), a recent UK-Canadian venture in Arctic Canada, has addressed these issues in order to place fundamental constraints on Earth structure beneath the Canadian Shield. The resulting data provide a tantalizing hint as to the processes that operated on the youthful Earth.