Black Sand Basin Boardwalk

Overview

This compact loop threads through one of Yellowstone’s most colorful corners—an outlying slice of the Upper Geyser Basin where brilliant pools and a lively creek-side geyser steal the show. The boardwalk is approximately 0.5 miles total, with short signed spurs, and takes most people about 30 minutes at a casual pace. Elevation gain is minimal (about 35 feet), and the walking is easy, though a few short sections are steeper.

Highlights on the Loop

Expect a quick hit of hydrothermal variety in a small footprint. Cliff Geyser often erupts right on the edge of Iron Spring Creek—bursts can reach up to roughly 30–40 feet and often repeat within minutes, so it’s worth lingering. Emerald Pool glows a deep green ringed by orange microbial mats; Rainbow Pool shows off colorful drainage channels; and Sunset Lake (technically a geyser) usually vents heavy steam that can hide its surface. Near the parking area, spurs and adjacent features include Spouter Geyser, Opalescent Pool, and Green Spring.

Geology and Color—What You’re Seeing

The basin takes its name from grains of black obsidian (volcanic glass) in the sand. Hot springs here circulate freely and typically don’t erupt; geysers have constrictions in their underground “plumbing” that build steam pressure and trigger eruptions. The vivid colors come from heat-loving microbes (thermophiles): colorless/yellow species thrive in the hottest water, while orange, brown, and green mats flourish in cooler runoff.

Logistics and Access

Black Sand Basin sits about 1 mile northwest of Old Faithful along the main road, with a signed pullout and parking lot. You can also walk about a mile from the Daisy Geyser area in the Upper Geyser Basin. The surface is almost entirely boardwalk; most visitors will find it easy, though a few short steep sections mean some wheelchair users may need assistance. Facilities at the pullout are minimal, so plan ahead.

Best Time to Visit

Anytime May–September is prime for an easy, colorful stroll. For photography, bright midday sun often makes the colors pop; on cool mornings, steam can shroud views—wait for a breeze or change angles. Cliff Geyser’s short cycles reward patience midday or afternoon. The basin is often less crowded than nearby marquee stops, making it a pleasant quick addition to an Old Faithful day.

Safety and Regulations

Thermal water can cause severe burns—stay on the boardwalk, supervise kids closely, and don’t run or push. Pets are not allowed on boardwalks or in thermal areas; trained service animals assisting individuals with disabilities are permitted. No special permit is required for the walk; standard park entry fees or a valid pass apply.