Move the numbers.
Morph a population pyramid through the demographic transition, walk a river from source to mouth, and find out why the same earthquake kills very different numbers.
Morph a population pyramid
FIG. 01 · MODELLED · DEMOGRAPHIC TRANSITION · 2.2Live births per thousand people per year. Falls when women are educated, contraception is available and children stop being farm labour.
Deaths per thousand per year. Falls first and fastest — clean water, sanitation and vaccination are cheap compared with changing family size.
Migrants are mostly young adults, so they bulge the middle of the pyramid — and their children widen the base.
What gets the marks. Nobody gets credit for saying "the pyramid is wide at the bottom". The credit is for reading a consequence off the shape: a wide base means schools, jobs and food demand in fifteen years; a top-heavy shape means a rising dependency ratio, pension and healthcare costs and pressure for pro-natalist or migration policy. Set the sliders to a country you have studied and check the shape matches your case study.
Walk a river from source to mouth
FIG. 02 · RIVER LANDSCAPES · LONG PROFILE · 1.3.3Drag from source to mouth. Everything in the Bradshaw model changes together — that is the whole point of it.
Slide towards bankfull storm flow. Velocity and the size of load the river can carry rise sharply — most erosion happens on a handful of days a year.
The trap this fixes. Students learn "the river speeds up downstream" and refuse to believe it, because the upper course looks faster. It looks faster because it is shallow, turbulent and full of boulders — friction. Downstream the channel is deeper and smoother, so the hydraulic radius rises and mean velocity rises with it, even though the gradient has collapsed. Exams reward the explanation, not the assertion.
Same earthquake, different death toll
FIG. 03 · MODELLED · TECTONIC HAZARDS · 1.1.2Each whole number is about 32 times more energy released. Magnitude is the hazard; it is not the disaster.
Shallow-focus quakes do far more damage: less rock between the focus and the people.
Exposure. A magnitude 8 under empty desert is a seismogram; the same event under a city is a catastrophe.
Money buys search-and-rescue, hospitals, insurance and the ability to rebuild — the whole right-hand side of the hazard management cycle.
Written codes are not enforced codes. This single slider does more to the death toll than magnitude does.
The comparison question. Every "compare the effects of two tectonic hazards" answer is really about this: hazard × exposure × vulnerability ÷ capacity to cope. Drop the development slider without touching magnitude and watch the death toll climb — that single move is the argument the mark scheme is waiting for, and it is why a richer country's earthquake costs more money and fewer lives.