It was recognised in the 1930s that temporal evolution of mantle convection should cause transient vertical motions of Earth’s surface, known as dynamic topography. Satellite-based observations of the gravity field were combined with early seismic tomographic images of the mantle to produce the first predictive models of dynamic topography in the mid-1980s. These predictions indicate very long-wavelength (>10,000 km) surface deflections, with peak amplitudes of 1-3 km. However, direct observations of dynamic topography necessary to test these predictions have proven difficult to isolate.
Over the last 20 years, the acquisition of modern seismic reflection and wide-angle refraction profiles in the oceanic realm has allowed detailed mapping of present-day dynamic topography, particularly along passive margins. The resulting anomalies are found to vary significantly over short lengthscales (~1000 km). Stratigraphic and geomorphological analyses indicate that these features can evolve on million year timescales, whilst seismic tomographic models suggest that much of this dynamic topography is related to flow in the shallow mantle immediately beneath the plates.
The North Atlantic Ocean provides an excellent case study for illustrating the diverse impacts of rapid upper mantle flow on the geological record. Thermal perturbations within the Icelandic plume conduit give rise to hot ripples that spread out within the plume head. Propagation of these ripples produces V-shaped ridges of thickened crust pointing down the Reykjanes spreading centre, ephemeral landscapes on fringing continental margins, and periodic shut-off of deep water currents flowing south from the Arctic Ocean. Dynamic topography is highly relevant to a wide-range of geological processes, ranging from sedimentary basin architecture and intraplate volcanism through to oceanic circulation and climate modelling.