Luis Alvarez 1911 – 1988.
The iridium layer, dinosaur death by meteorite impact, and subatomic particle discoveries.

Anaximander c. 610 BC – c 546 BC.
An ancient scientific revolution: the first person in history to recognize that our planet is free in space and does not need to sit on something; produced one of the first ever maps of the world.

Mary Anning 1799 – 1847.
Ancient animals, fossils, and paleontology: discovered the first complete specimen of a plesiosaur; deduced the diets of dinosaurs.

J Harlen Bretz 1882 – 1981.
After decades of ridicule from uniformitarian geologists established that immense, cataclysmic floods created extraordinary landscapes in America’s Pacific Northwest.

James Croll 1821 – 1890.
Provided the first mechanism accounting for ice ages; said climate change is caused by periodic changes in Earth’s orbit affecting the amount of energy received from the sun; devised the concept of ice-albedo feedback.

Georges Cuvier 1769 – 1832.
Father of paleontology; species extinction; master of comparative anatomy – established that a fossil he named pterodactyl was a flying reptile; promoted the theory of catastrophism; argued species were fixed and did not evolve.

Eratosthenes c. 276 BC – c. 194 BC.
Accurately calculated Earth’s size 2,500 years ago; founded the science of geography; and devised the famous prime number sieve.

Stephen Jay Gould 1941 – 2002.
Paleontologist who devised the theory of punctuated equilibrium, which proposes that evolution consists of long periods of stability broken by shorter periods of rapid change. An award-winning author and popularizer of science.

Jack Horner Born 1946.
Popularizer of science: discovered that dinosaurs cared for their young and some nested in colonies. Working on reactivating dormant dinosaur DNA to hatch a modern-day dinosaur.

James Hutton 1726 – 1797.
Founded modern geology. Found our planet is very much older than previously believed; devised the principle of uniformitarianism, which says our world was shaped by natural processes such as erosion and deposition; stated the theory of evolution by natural selection before Darwin was born.

Inge Lehmann 1888 – 1993.
Analyzed earthquake waves to discover that within our planet’s liquid core, at the earth’s center, there is a solid core whose diameter is greater than 1,000 km.

Matthew Maury 1806 – 1873.
A founder of modern oceanography; mapped the North Atlantic Ocean floor, discovering a submarine mountain range – part of the Mid-Atlantic Ridge; invented the ‘electric torpedo,’ the most devastating naval weapon of the American Civil War.

John Michell 1724 – 1793.
First to suggest earthquakes are caused by movements of rocks miles below Earth’s surface and travel long distances as waves; invented the torsion balance to weigh our planet.

Milutin Milanković 1879 – 1958.
The first science-based climate predictions for the other rocky planets; Milankovitch cycles offer a robust mathematical explanation of recurring ice ages and climate change based on Earth’s orbital changes.

Gene Shoemaker 1928 to 1997.
The first astrogeologist and a founder of planetary impact science; proved large craters on Earth were caused by collisions with asteroids and comets rather than volcanic activity; proposed microscopic life could travel between planets on rocks blasted into space by asteroid impacts.

Nicolas Steno 1638 – 1686.
A founder of modern geology; established some of its fundamental principles, including the law that the oldest layers of rock are found below younger layers.

Harold Urey 1893 – 1981.
Discovered deuterium; showed how isotope ratios in rocks reveal past Earth climates; founded modern planetary science; the Miller-Urey experiment demonstrated that electrically sparking simple gases produces amino acids – the building blocks of life.

Alfred Wegener 1880 – 1930.
Discovered continental drift, proposing that our planet once consisted of ocean surrounding a single great continent he called Pangea that split apart over many millions of years to form the continents we see today.