Rock which floats

How does the ironwood stick compare to the regular wood stick? How does the pumice stone compare to the regular rock? How could you measure the relative densities of unknown objects? Details Activity Length 10 mins. This demonstration introduces the students to the idea that large objects do not necessarily have a higher density than small objects Density depends on how much mass is packed into a given volume i.

Objectives Demonstrate how the distribution of particles in a substance determines its density. What To Do Show the students the two sticks and two rocks. Ask them to predict what will happen when each object is placed in the water. Ask them what they base their predictions on. Put the objects in the water individually or as pairs. Surface tension serves to keep these bubbles locked inside for prolonged periods.

The bobbing observed in laboratory experiments of pumice floatation is explained by trapped gas expanding during the heat of day, which causes the stones to temporarily float until the temperature drops. Manga has also used an X-ray technique at the ALS called microdiffraction, which is useful for studying the origins of crystals in volcanic rocks. The recent study triggered more questions about floating pumice, Fauria said, such as how pumice, ejected from deep underwater volcanoes, finds its way to the surface.

That stone was recovered from the sea floor in the area of an active underwater volcano by a research expedition that Fauria and Manga participated in. Underwater volcano eruptions are not as easy to track down as eruptions on land, and floating pumice spotted by a passenger on a commercial aircraft actually helped researchers track down the source of a major underwater eruption that occurred in and motivated the research expedition.

Pumice stones spewed from underwater volcano eruptions vary widely in size but can typically be about the size of an apple, while pumice stones from volcanoes on land tend to be smaller than a golf ball. This volcano erupted completely different than we hypothesized. Our hope is that we can use this one example to understand the process. Scientists think that pumice rafts like these have helped life-forms cross open oceans and start new colonies in new places.

Much the way humans did on rafts of our own making. Synopsis: In August , several groups of sailors were surprised to find themselves sailing through rocks as far as the eye could see. It was pumice that had been extruded from a subsea volcanic vent near Tonga and had accumulated into a raft the size of Manhattan.

The raft is headed toward the Great Barrier Reef carrying organisms that may bring new life to the reef. Some scientists suggest that rafts such as this one were instrumental in the distribution of life-forms around the planet.

Discover the natural wonders of Earth on over radio stations nationwide. Floating Rocks. Download PDF zip file. This raft of pumice floating west of Tonga in the South Pacific is the size of Manhattan Island inset. In , one formed off the coast of New Zealand that was miles long.

Background: Floating Rocks Synopsis: In August , several groups of sailors were surprised to find themselves sailing through rocks as far as the eye could see. Pumice forms when molten igneous rock is ejected at high pressure from a volcano, similar to the whipped cream that comes from a pressurized can. When the explosion releases the pressure, the foamy mass cools suddenly, freezing the air bubbles in place, creating a lightweight, low-density rock filled with air bubbles.