Construction by Destruction 

Unlike the incremental changes caused by weathering and erosion, some geologic process have changed Joshua Tree’s landscape in short, violent events.  

Malapai Hill 

Volcanic Origins: Standing tall above Queen Valley to the west, the hard, black basalt of Malapai Hill weathers and erodes slowly. This volcano is much younger than the surrounding monzogranite and likely formed within the past 15 million years. 

Blue Cut Fault 

Ancient Earnt Valley: Located to the south southwest, there has not been an earthquake on this fault in the last 8,000 years, but it is still active and could generate a moderate earthquake. One of many fault lines in the park, the Blue Cut Fault extends for over 50 miles (80 km) through the heart of the park. Earthquakes on this fault have resulted in over four miles of offset over the last few million years, with the north side of the fault moving west and the south side moving to the east and the uplift of the Hexie Mountains along the northern edge of Pleasant Valley.

Exploration Area  

Explore the ancient remnants of a volcano with desert views —hike to the top of Malapai Hill or around its base. Do not attempt during high temperatures. 

Glossary 

Erosion: A geological process in which natural forces such as wind or water move natural materials like rocks, dirt, and sand.  

Weathering: natural process when water, wind, heat, plants and other forces, slowly break or change the rock. 

Basalt: A dark fine-grained volcanic (i.e. igneous) rock.  

Uplift: The elevation of the Earth’s crust. Usually referring to tectonic uplift caused by slowly moving plates that cause earthquakes and changes to the earth’s surface.