- Purple - "All-Canadian" Route. Sold as a wagon route over flat prairie, it led instead 1,500 miles through unimproved wilderness.
- Black - Ashcroft Route. Skirted the Canadian Rockies through an interior rainforest, that was almost impassable.
- Blue - "All-American" Routes. Shortest routes to Klondike but led directly over glaciers. Dangers included crevasses, snow-blindness, starvation, and freezing due to lack of fuel for fires in the middle of the ice.
- Green - All-Water "Rich-Man's" Route. Steamships sailed around Alaska and 2,200 miles up the Yukon River. Easiest, most expensive route. Impassable for eight months a year when river was frozen. Red - "Trail of '98." Steamship trip up Inside Passage to Skagway, followed by approximately 40-mile hike over Chilkoot or White Passes to Bennett Lake, source of Yukon River. Floated remaining 500 miles downriver to Dawson City.
Geologists have studied gold deposits for decades and know of different processes that form gold deposits. Klondike gold formed by one of these processes. The gold in the Klondike is known as orogenic gold. The word “orogenic” refers to a mountain-building event. Orogenic gold is gold that formed during a mountain-building event. Mountain-building events generate large amounts of heat and pressure, so oftentimes metamorphism will accompany this process. Years of geologic research have shown that orogenic gold is usually hosted in metamorphic rocks. This does not mean that all metamorphic rocks have orogenic gold, or that every mountain-building event leads to gold deposits. It just means that the orogenic gold that has been found was found in metamorphic rocks.
But how does the gold get into the metamorphic rocks? During metamorphism, minerals get squeezed and heated to the point where they release really hot fluids. These fluids flow upwards through the crust towards the surface of the Earth. As they flow upwards, they dissolve other minerals that they pass by and carry those dissolved chemical elements with them. Gold is included in very small amounts in some minerals, so if the fluid dissolves a mineral with a little bit of gold, the fluid will also contain a little bit of gold. These fluids seek weaknesses in the rocks, such as faults, as a pathway to flow along. Eventually, the fluid will encounter different environmental conditions that cause it to deposit the gold and other elements it was carrying as a solid.
Orogenic gold deposits often occur in veins, which are long and skinny sheets of gold and other minerals, such as quartz, within a rock. Sometimes veins will trace fault lines or other weaknesses because these are the easiest paths for the gold-bearing fluid to follow.