Whenever we drive from Riyadh to Madina, we've always wondered about the sudden black terrain that we hit near the outskirts of Madina. The shift is quite dramatic, from the expected light-colored sand and dirt that we see most of the way to the pitch-black lava fields that suddenly surround both sides of the highway.
And so it was pretty cool when I stumbled upon this satellite image of the area:
"The western half of the Arabian peninsula contains not only large expanses of sand and gravel, but extensive lava fields known as haraat (harrat for a named field). One such field is the 14,000-square kilometer Harrat Khaybar, located approximately 137 kilometers to the northeast of the city of Al Madinah (Medina). According to scientists, the volcanic field was formed by eruptions along a 100-kilometer long north-south linear vent system over the past 5 million years; the most recent recorded eruption took place between 600 - 700 A.D. Harrat Khaybar contains a wide range of volcanic rock types and spectacular landforms, several of which are represented in this view."