Norris Geyser Basin is the hottest and most changeable thermal area in Yellowstone.  We will explore many of the features you would see if you walked the 2 1/4 miles (3.6 km) of trails.  Discover the location of the tallest active geyser, colorful hot springs, and microscopic life in one of the most extreme environments on earth.

Echinus (e-KI-nus) Geyser was a perennial crowd-pleaser which typically erupted every 35 to 75 minutes. Late in 1998 this geyser altered its interval and now erupts only a few times per day at best. Its pool fills gradually with water; then suddenly, bursts of steam and water explode 40 to 60 feet (12 to 18 m) skyward.  Eruptions usually last about 4 minutes but in the past major eruptions have lasted as long as 118 minutes. The major eruptions were believed to be caused by a secondary water source which has mysteriously vanished.  There has not been a major eruption in 3 years. In late 1998 Echinus' performance diminished and became erratic. As of mid-1999 its eruptions remain unpredictable.

Echinus is the largest acid-water geyser known.  Its waters are almost as acidic as vinegar with a pH ranging from 3.3 to 3.6 .  Acid geysers are extremely rare with the majority of the planet's total being found here at Norris Geyser Basin.

The world's tallest active geyser, Steamboat can erupt to more than 300 feet (90m), showering viewers with its mineral-rich waters.   For hours following its rare 3 to 40 minute major eruptions, Steamboat thunders with powerful jets of steam.  As befitting such an awesome event, full eruptions are entirely unpredictable.  Recently, Steamboat had one major eruption on May 2, 2000.

More commonly, Steamboat  has minor eruptions and ejects water in frequent bursts of 10 to 40 feet.

A hot spring's color often indicates the presence of minerals.  In a clear blue pool, the water is absorbing all colors of sunlight except one, blue, which is reflected back to our eyes.  Here in Emerald Spring's pool, another factor joins with light refraction to give this spring its color.  The 27-foot (8 meter) deep pool is lined with yellow sulfur deposits.  The yellow color from the sulfur combines with the reflected blue light, making the hot spring appear a magnificent emerald green.

Hot spring water can dissolve and transport sulfur from underground.  The mineral can deposit and crystallize at the earth's surface, sometimes in hot spring pools.