美国国家公共电台 NPR PHOTOS: The Creamy, Sculpted Dunes Of White Sands National Monument

LOURDES GARCIA-NAVARRO, HOST:

White Sands National Monument in southern New Mexico is a huge expanse of pure, white sand dunes 2 that form a shifting, spectacular landscape. Here's NPR's Melissa Block with the latest in her series Our Land on a place like no other on the planet.

MELISSA BLOCK, BYLINE 3: When we put out a call on social media asking for ideas of places we should go in New Mexico, a bunch of people said, you've got to go to White Sands. OK - twist my arm.

MARIE FRIAS SAUTER: So who would like to go out on the dune 1?

BLOCK: We would.

FRIAS SAUTER: OK, let's do it (laughter).

UNIDENTIFIED WOMAN #1: Yeah.

BLOCK: We hike up into an other-worldly landscape - picture bright white sand dunes, like creamy sculpted 4 waves, rippling 5 and rolling for miles off to the horizon.

FRIAS SAUTER: Maybe like snowfields...

BLOCK: We're with White Sands superintendent 6 Marie Frias Sauter.

FRIAS SAUTER: ...Frosting on a white cake.

BLOCK: Cobalt-blue sky above and, far in the distance, purple mountains that ring at this desert basin.

FRIAS SAUTER: As the sun goes down and slants 7 more on an angle, it becomes just a play of shadows, just light and dark and light and dark. And it's just gorgeous.

BLOCK: Imagine you're park ranger 8 Eugene Ibarra, and this is your office.

EUGENE IBARRA: Being here inside the dune field is like if you're in another planet. It's so alien-like. The only thing that reminds you that you're still in planet Earth is that the sky is blue.

BLOCK: The sun is broiling 9 hot, but the White Sands stay cool under our bare feet.

IBARRA: It can be over a hundred degrees and it won't burn your feet. The sun is white, so it reflects back the heat in the sun.

BLOCK: It's a white and super soft.

IBARRA: Softer than sugar.

FRIAS SAUTER: Yes.

BLOCK: You're rubbing it in your hands now.

FRIAS SAUTER: Yeah (laughter). It's like powdered sugar.

BLOCK: The dunes are made of the soft mineral gypsum, laid down 250 million years ago when the southwestern U.S. was covered by the Permian Sea. Later, that seabed was pushed up into the mountains that surround us.

IBARRA: Do you see those white bands across the mountains?

BLOCK: Oh, yeah.

IBARRA: Those are gypsum deposits.

BLOCK: Rainfall dissolves those deposits, carrying the gypsum down and replenishing the sand dunes, which shift constantly with the winds.

FRIAS SAUTER: It's very easy to get lost out here. And, you know, people have died out here in the dunes.

BLOCK: How often does that happen?

FRIAS SAUTER: Too often.

BLOCK: In fact, it happened two summers ago.

FRIAS SAUTER: We lost a couple - a mother and a father, husband and wife - who came out in August and hiked in the afternoon the Alkali Flat trail. And they did not survive. Their son did, but they did not so...

BLOCK: What happened?

FRIAS SAUTER: They didn't have enough water. And they underestimated the difficulty of the trail and hiking on a hot August afternoon.

BLOCK: There are signs warning that there's no water available beyond the visitor's center. But it's easy to forget just how unforgiving this park can be because it's so beautiful.

I watched sisters Belen and Lourdes Materon - visiting from Houston - as they play in the sand, letting it drizzle 10 through their fingers.

UNIDENTIFIED GIRL #1: Can I tell you something about this? Sometimes when you look close to it, it looks like little crystals.

UNIDENTIFIED GIRL #2: It's weathered crystals.

UNIDENTIFIED GIRL #1: It's super sparkly and pretty and nice.

BLOCK: And if you're used to staying off of sand dunes to protect them - not here. At White Sands, dune sledding is encouraged.

UNIDENTIFIED GIRL #1: Three and go.

BLOCK: The park service even sells plastic flying saucers in the gift shop. I get some sledding pointers from 9-year-old Antonio Pina.

ANTONIO: The trick is, if you're going to stand up, keep it low, or you can just sit down.

BLOCK: Sounds like a plan. OK, Melissa Block, about to go sledding at White Sands National Monument in New Mexico. Here we go. Awesome 11 - stuck the landing.

ANTONIO: Nice.

(SOUNDBITE OF PRIMUS SONG, "LAST SALMON MAN")