Week 3 Discussion

In the context of painted landscapes, the concept of "rocks" is flexible. For this unit, here are a couple of photos to help to clarify what is meant by a rock.

The mountain is Japan's Mt. Fuji.

Here is another pair of photos to help further refine the idea.

The distinction is that rocks are like stones in the first photo above or distinctive landscape features like Half Dome. Generalized landscape features, no matter how attractive, like mountains and colorful hillsides, are not rocks for the purpose of this discussion.

The Japanese language has two words for rocks. Ishi is a word used for regular or small stones like those in the first photo set on the left above. Iwa is used for large, solid rocks, boulders, or crags like Half Dome. Just to be clear. both photos below are showing rocks. That includes Zion's canyon walls.

Types of Rocks

When biologists speak of living, organic entities like birds, fungi, moss, etc. they mean things made up of various kinds of cells. When geologists speak of such non-living, inorganic, solid things like the ones in the photos above, they mean things that are composed of various kinds of minerals. Minerals are solid substances that have a definite chemical composition and an orderly internal crystal structure. Two of the most common minerals are feldspar and quartz. In this photo, feldspar is on the left and quartz is on the right.

Igneous Rock

Igneous rocks are ones that start off very hot and liquid. Molten rock underground is magma. Molten rock above ground is lava. Common types of igneous rock are granite and basalt. Granite forms very slowly underground. Basalt generally comes from lava. Because granite cools very slowly, the chemicals that comprise minerals tend to draw together and form crystals large enough to be seen with the naked eye. When granite cools very very very slowly, its mineral crystals can be as much as an inch or more across. This form is called pegmatite. 

Basalt cools so rapidly that its minerals never have a chance to grow large enough to be seen with the naked eye. Cooling is often so rapid that gases that are mixed with lava can't escape before the lava hardens into rock, trapping many tiny bubbles inside. Pumice is an extreme case in which there are so many bubbles and so little actual rock that it can float on water. Obsidian is at another extreme, cooling so rapidly with no trapped gas that it literally forms a volcanic glass. Broken chards of obsidian can be so sharp that it is easy to be cut by them. Native Americans used to make arrow heads from it.

Sedimentary Rock

Sedimentary rock is rock that is comprised of layers of material that has fused together with time and pressure. The source of the material can be other rocks that have been ground down and been transported via erosion to somewhere to settle down, like lake beds or the ocean floor. The passage of geologic ages can lift the layers and bend and fold them in various ways. This sedimentary sandstone in northern Arizona is called The Wave.

Other common types of sedimentary rock are shale, chalk, gypsum, chert, and travertine. Conglomerate is a sedimentary rock that has a mixture of different sized material from silt to pebbles embedded in it.

Metamorphic Rock

Metamorphic rock is rock that starts out as one kind of rock--igneous or sedimentary or metamorphic. Underground, after it is under extreme heat and pressure without melting for a long period of time, it is transformed into another kind of rock. The minerals in the parent rock recrystallize into different kinds of minerals. For example, some types of limestone transform into marble. Then with the assistance of a sculptor, it becomes Venus de Milo.

Both limestone and marble suffer from the same problem. Acid rain from modern pollution eats away at both.

The gneiss (pronounced "nice") pictured above can originally come from granite (an igneous rock) or shale (a sedimentary rock). Basalt and gabbro (igneous rocks) can turn into greenschist, amphibolite, or eclogite. Shale (a sedimentary rock) turns into slate when it doesn't become gneiss, and sandstone turns into quartzite. There are many other kinds of transformation.

More Rock Features

All of this barely touches the surface about rocks. If this were a geology class, we could spend a whole semester talking about nothing but rocks and still not cover everything. This section touches on a few selected additional rock features.

The first two have to do with rocks keeping a record of past events. The first photo shows that after the sedimentary rock was formed, an earthquake happened; perhaps two. The amount of slippage is recorded by the fault lines that were captured in the rock. The second photo shows preexisting cracked rock into which magma flowed (an intrusion) and eventually solidified into a different kind of rock. The photo shows that two different intrusions occurred at different times. Can you figure out what the sequence of events was?

The next feature is a geode. They often start in cooling lava in which gas bubbles form hollow spaces. Then mineral-rich water seeps in. When the water evaporates, it leaves behind a crystalline inner lining. The lining is a mineral, not a type of rock. The mineral in this photo is probably quartz. Agate is very common. Geodes are not naturally open like this. They are sawn open.

Erosional Features

On a larger scale, rocks can be part of very interesting landscapes. Here are some erosion created examples.

Devil's Tower

Devils Tower (Devils Tower National Monument, Wyoming) is a volcanic plug. Magma filled up the throat of a volcano and then stayed there, solidifying in place. Eventually, the softer mountain material surrounding it eroded away, leaving behind the plug.

Mushroom Rocks

These are found in many areas around the world. They are most often formed by wind-blown sand, blasting away at soft rock layers that are capped by more resistant upper layers. This one is located in northern Arizona.

Sea Stacks

Sea stacks are tall, vertical columns of rock standing in the ocean near a coast, separated from the main shoreline. Water erodes away the stuff around it. This one is located at Hvítserkur, Iceland.

Artwork

Japanese Gardens

Lafcadio Hearn, a western writer who moved to Japan in 1890, once wrote that, "to comprehend the beauty of a Japanese garden, it is necessary to understand the beauty of stones." The garden here is located on the grounds of Nijō-jō, the castle home of Ieyasu Tokugawa in Kyōtō, Japan.

Suiseki

Suiseki is a form of rock art that literally means water stone. (Sui means water, and seki is a sound that has the same meaning and kanji as ishi but is never used alone.) It is the traditional Japanese art of appreciating small, naturally formed rocks that evoke the shape of natural landscapes, objects, or abstract forms. Collectors look for dark, weathered stones with a sense of age, stability, and quiet elegance. The rocks found for display are not to be altered in any meaningful way, and are displayed on a platter or pedestal.

Japanese interest in suiseki, tea gardens, and bonsai all rose at about the same time. Bonsai and suiseki are often displayed together to form miniature landscapes.

Zen Rock Gardens (Sekitei)

Sekitei first became popular in the Kamakura Era (1185-1333) following the arrival of Zen Buddhism from China in the late 13th Century. These gardens continued to evolve in the following centuries. Zen emphasized the importance of meditation, as well as a simpler, more mindful outlook. Such rock gardens generally have strategically placed rocks surrounded by raked pebbles.

This sekitei is located in Diakokuji Temple, Kyōtō, Japan. One possible interpretation is of islands surrounded by ocean waves.

This garden is located at Zenkōji Temple in Nagano, Japan. Think of a scene from above a cloud layer. Can you see the dragon's head starting to rise through it?