Geology: what the ground is doing
The map is not finished. Plates move at roughly the speed a fingernail grows, which is slow enough to ignore and fast enough that it has moved measurably since the last time the borders were drawn. Occasionally it happens all at once.
Which country has the most active volcanoes?
Indonesia
Indonesia has roughly 130 active volcanoes, sitting where three tectonic plates meet along the Ring of Fire. Its 1815 Tambora eruption caused a year without a summer in Europe.
Source: Smithsonian Global Volcanism Program
Roughly when did Pangaea begin to break apart?
About 200 million years ago
The supercontinent began rifting in the early Jurassic, around 200 million years ago. The Atlantic has been widening ever since, at roughly the rate fingernails grow.
Source: Standard plate tectonic reconstructions
How fast is the Atlantic Ocean widening?
A few cm a year
Sea-floor spreading at the Mid-Atlantic Ridge pushes Europe and North America apart at roughly the speed fingernails grow (a few centimetres a year), measurable by GPS.
Source: NASA GPS geodesy; NOAA seafloor spreading rates
Iceland is unusual because it sits on what?
Two tectonic plates
The Mid-Atlantic Ridge runs right through it, so Iceland is pulling apart. You can walk between the North American and Eurasian plates at Thingvellir.
Source: Icelandic Institute of Natural History
How deep is the deepest hole ever drilled into the Earth?
About 12 km
The Kola Superdeep Borehole reached about 12,262 m over twenty years. That is a tiny fraction of the roughly 6,371 km to the centre, under a five-hundredth of the way.
Source: Soviet Kola drilling project records
Where are the oldest known rocks on Earth's surface found?
Canada
The Acasta Gneiss in the Northwest Territories is around 4 billion years old, and rocks in northern Quebec may be older still. Ancient crust survives on stable shields, not active margins.
Source: Geological Survey of Canada radiometric dating
Where is the largest canyon on Earth?
Greenland
Radar surveys found a canyon roughly 750 km long beneath the Greenland ice, longer than the Grand Canyon. Above ground, Tibet's Yarlung Tsangpo gorge is deeper than Arizona's.
Source: NASA Operation IceBridge radar surveys, 2013
Which is the largest salt flat in the world?
Salar de Uyuni, Bolivia
About 10,600 km2 and so flat that it varies by under a metre across its whole extent. Satellites use it to calibrate altimeters, and it holds a large share of the world's lithium.
Source: Bolivian geological survey; NASA satellite calibration use
What is the magnetic north pole doing?
Drifting towards Siberia
It has moved from Arctic Canada towards Siberia, accelerating to around 50 km a year at times. Navigation models have to be updated more often than the usual five-year cycle.
Source: NOAA and British Geological Survey World Magnetic Model
Why do different countries teach different numbers of continents?
The boundaries are conventions
Many English-speaking countries teach seven; much of Europe and Latin America teach six, merging the Americas; some teach five. Europe and Asia are one landmass under any physical test.
Source: Comparative national curricula