The land that later became Juneau looked a lot different in the 1870s, before western settlers began searching the area for gold. Much of what became downtown was a muddy tidal flat. Much of what became the Mendenhall Valley was under glacial ice or ocean water. Since then, glaciers, weather, silt, earthquakes and human hands have changed the land.
Glaciers carve valleys and push up stony ridges called morraines.
They also move large boulders called erratics. Ice gradually fragments erratics into smaller rocks. Rain carves out creeks and riverbeds, washing silt to larger bodies of water. And then the process may begin all over again a few thousand years later. Downtown Juneau is built on two land forms - an alluvial fan created by Gold Creek, and an ancient delta, said Kathy Hocker, a naturalist with Juneau's Discovery Foundation.