Deep Time Elevator Game

A lift drops down a shaft cut through twelve bands of rock, one for each period of the Phanerozoic, the last 539 million years of Earth's history. At each floor the doors open beside a fossil from that time: a mammoth's tusk near the top, a Tyrannosaurus skull further down, and a trilobite at the bottom. Name the period and its plate fills in with the date it began. It is a memory palace turned on its side: the same journey, in the same order, every time.

How to play

1. The lift drops from the surface through the rock. Each floor is one geologic period, the youngest at the top.
2. At each floor the lift stops beside a fossil from that period. It is your hint.
3. Press the period's button on the lift panel. The twelve buttons are shuffled at every floor, and a button's lamp lights once its floor is named.
4. A right answer fills in the floor's plate with its start date, and the lift drops on. A wrong answer costs a life, and the lift waits. 3 lost lives end the ride.
5. Reach the Cambrian, twelve floors down, and the lift rides back up past every plate.

Start dates mode shows each floor's name and asks when its period began, from four dates. On a keyboard, type the first letters of a period's name until one button is left, then press Enter. In Start dates mode, press 1 to 4. Escape or Space pauses. Sound starts off on a first visit.

Scoring

• A right answer scores 100 points.
• Each right answer in a row before it adds 20, so the second in a row scores 120, up to 200 for the sixth in a row and every one after it.
• A wrong answer ends the run of right answers.
• Reaching the bottom scores 100 for each life you have left, outside practice.

Your five best scores in each mode are saved in this browser, with the floor each game reached. In practice no lives are lost, so the ride always reaches the bottom. End it from the pause screen. Practice games are not saved.

The periods and their dates

The dates are the International Commission on Stratigraphy's, from its International Chronostratigraphic Chart, version 2026/06, rounded. From the top: the Quaternary began 2.6 million years ago, the Neogene 23, the Paleogene 66, the Cretaceous about 143, the Jurassic 201, the Triassic 252, the Permian 299, the Carboniferous 359, the Devonian 420, the Silurian 443, the Ordovician 487 and the Cambrian 539. The Cretaceous is marked about because geologists have not yet agreed on a golden spike, the point in a rock face that marks where a period begins, for its base. Some of these dates have moved in recent years, so an older book may give 145 for the Cretaceous or 485 for the Ordovician.

Ways to remember the order

A lift going down is a memory palace with twelve rooms in a fixed order, and each fossil is the picture in its room. Make the pictures act on the period's name: a mammoth in a quarry for the Quaternary, a giant insect like a dragonfly over a coal seam for the Carboniferous. Once the order holds, the dates are numbers, and the Major System turns each into a word you can add to its floor, as in memorizing historical dates with a memory palace.

Try our other free memory games.