In the Northwest we don’t have just sandy beaches. We have rocky promontories encrusted with exotic life forms. We have sand flats where hidden squirters express their enthusiasm with two foot fountains; sloughs where each cup of mud contains a hundred living things; winding estuaries spawning myriads of newborn creatures that crawl, burrow, swim, or fly on to their greater destinies. Inquisitive persons often celebrates the low tides of summer with family expeditions to local beaches where experienced marine biologists often help budding scientists understand the life around them. Nothing is needed except curiosity and a spare pair of dry socks.
Rocky beaches to the west of Port Angeles abound with crystal clear tide pools and beautiful, other-worldly marine life. The goal of a good observer is to learn without harming any living thing. So we look, take notes and pictures, and sometimes look under rocks in the inter-tidal zone, being careful to replace them as they were originally. It is always interesting to see how an animal protects itself from predators or from the air and sun at low tide. Mussels and barnacles shut their doors tight and survive in the hot sun for hours. Small fish flee from a shadow to safety under a rock. Feather duster worms retract in a flash into their tube homes when they detect a disturbance in the water. Caught out of water by the receding tide, sea stars stop moving and hunker down in their tough skins close to the rocks to conserve their water. They casually flaunt their bright colors because land animals don’t like their taste. Their primary enemy is another starfish, the sunstar. You may see the many-legged sunstars lurking just outside the low tide level. These omnivorous ogres are too bulky and soft to survive for long out of water, so they rarely venture into the shallows.
A biologist will tell you that starfish belong to the echinoderm family, and that there are other members, too. Echinoderm means spiny skin. A good observer will note that most sea stars have five arms with many tiny legs on the underside. Each leg has a tiny sucker on the end that holds things and tastes them at the same time. These are called tube-feet. Submerged sea stars seem to glide over the bottom, with hundreds of tube-feet somehow working together to get the star to its destination. The suckers enable the star to hold its place even when the waves are very forceful. Only a few stars get caught in high waves without a firm grip on an anchoring rock. Their dried bodies are sometimes found entangled with driftwood and other flotsam above the high tide mark.
Where are the other echinoderms? Look for tube-feet in unlikely places. Such as under a red or green sea urchin or under a dark red sea cucumber. Sea cucumbers are easier to pick up than sea urchins, and their tube-feet are obvious. There are big red sea cucumbers and small white ones out in the open, and red ones that live under rocks with only their feathery feeding plumes showing. Quite different in appearance and behavior, but all belong to the sea cucumber family. If you also discover that both the sea urchin and the sea cucumber have five segments, like the sea star, then you may be confident that you have discovered more members of this interesting family of invertebrates. Echinoderms are important to the health of Puget Sound because they spend their lives cleaning up organic debris. Sand dollars are also in this family, but are less likely to be found on rocky beaches.
Where waves and currents are strong, rocks provide an essential anchor. Various species invent unique ways to hold their places. Barnacles and rock scallops use a permanent water-proof cement to stake their claim. Mussels use an amazingly strong glue and many small, tough organic threads that can be replaced if broken. Slow moving limpets, snails, chitons and abalone (yes we have abalone here) rely on a strong foot for suction to hold them in place.
Other shellfish abound. Cockles, scallops and various clams are found in sandy areas between the rocks. Surprisingly, fossils of some of these shellfish may be found in the nearby sandstone cliffs. There is nothing like the thrill of cracking a rock with a hammer and chisel and finding a perfect scallop shell inside! Grey, rounded fossil nodules are common. Many nodules are formed around a piece of organic material: a leaf, a crab claw, a crinoid stem, or a shell. As the soft organic material decomposes in the mud it gives off chemicals that harden the mud around it, eventually forming the rock nodule.
Fossil Crab in Natural Rock Nodule – Photo by Lyon McCandless
Many beach rocks have interesting stories to tell. Look for a fist-sized dark gray or black rock with white spots. You may be able to see wood grain or tree rings on the end, indicating that it is probably a piece of petrified wood. The white spots are actually the burrows of Toredo worms, now filled with a white mineral. You can be sure that this rock has had some interesting adventures.
It was once part of a living tree growing on dry land, breathing air and drinking fresh water. The fact that the rock exhibits wood-like grain and tree rings indicates that it was once a part of a deciduous tree. (Probably of the Cenozoic Era rather than the older Paleozoic or Mesozoic Eras which were dominated by giant ferns.) Except for sub-tropical salt water mangroves, most deciduous trees depend on fresh water in the atmosphere and ground. The fossil’s closely spaced tree rings indicate relatively slow growth in a climate with seasonal changes and an atmospheric makeup similar to the current one. A warmer atmosphere with higher CO2 content would result in wider growth rings.
The tree probably grew quite close to the ocean because eventually a fairly large piece of it was submerged in salt water. It may have been transported by a land slide. It must have stayed in salt water less than 100 feet deep for at least six months to become so infested with boring Toredo worms. Toredos, sometimes called the bane of wooden ships, look like a worm, but are a type of mollusk that burrows into wood instead of sand. What would be a shell in other mollusks has moved to the end of the Toredo and changed into jaws that gnaw into the wood.
The tree eventually sank to the sea bottom where it joined clamshells and crabs that were slowly being covered with mud and sand. And as the years went by it was buried so deep that the surrounding sand and clay became cemented together in a form of sandstone. Hot, mineralized water replaced all the wood fibers with stone, and filled the worm holes with calcite crystals.
Fossilized Wood with Toredo Holes – Photo by Lyon McCandless
The creation of a stony fossil requires heat, water and pressure. A burial depth of 500 feet or more would heat the water that fills the small spaces in the rock and would dissolve many of the minerals present. Subsurface water moves slowly through the pores of even relatively dense rock due to crustal flexing and changing tidal pressures. The water first saturates the wood and then gradually breaks down the softer parts and replaces them with silicates in a process called ‘permineralization’. The worm burrows were probably filled quickly with the relatively soluble calcite, and later on the wood itself was slowly replaced with another mineral.
Finally the slow movements of the earth’s tectonic plates lifted the whole layer of sandstone thousands of feet. Now above sea level, the thick layers of sedimentary rock were exposed to the forces of rain and weather. And the seemingly solid rock cliffs continuously crumble, bringing rocks and fossils to light for the first time in thousands of years, reminding us that nature is change.
Fossil wood with worm holes may be found adjacent to the cliffs on the south side of the straits of Juan de Fuca. The relatively soft sandstone cliffs slough off and weather away leaving harder rocks on the beach. Several types of fossil clams and fossil crabs are found near the fossil wood both in the sandstone cliffs and on the beach. These support the assumption that the sandstone is the original matrix in which permineralization occurred.
Fossil rocks with rounded edges indicate abrasion by wave or alluvial action. Nearby very similar pieces of petrified wood may be more jagged, more wood-like in appearance. Some do not have worm holes. The jagged samples must have weathered from the cliffs recently, while the rounded rock has been tumbled by wave action. New material is coming out of the cliffs all the time, just waiting to be discovered by some inquisitive person.
Rocky beaches to the west of Port Angeles abound with crystal clear tide pools and beautiful, other-worldly marine life. The goal of a good observer is to learn without harming any living thing. So we look, take notes and pictures, and sometimes look under rocks in the inter-tidal zone, being careful to replace them as they were originally. It is always interesting to see how an animal protects itself from predators or from the air and sun at low tide. Mussels and barnacles shut their doors tight and survive in the hot sun for hours. Small fish flee from a shadow to safety under a rock. Feather duster worms retract in a flash into their tube homes when they detect a disturbance in the water. Caught out of water by the receding tide, sea stars stop moving and hunker down in their tough skins close to the rocks to conserve their water. They casually flaunt their bright colors because land animals don’t like their taste. Their primary enemy is another starfish, the sunstar. You may see the many-legged sunstars lurking just outside the low tide level. These omnivorous ogres are too bulky and soft to survive for long out of water, so they rarely venture into the shallows.
A biologist will tell you that starfish belong to the echinoderm family, and that there are other members, too. Echinoderm means spiny skin. A good observer will note that most sea stars have five arms with many tiny legs on the underside. Each leg has a tiny sucker on the end that holds things and tastes them at the same time. These are called tube-feet. Submerged sea stars seem to glide over the bottom, with hundreds of tube-feet somehow working together to get the star to its destination. The suckers enable the star to hold its place even when the waves are very forceful. Only a few stars get caught in high waves without a firm grip on an anchoring rock. Their dried bodies are sometimes found entangled with driftwood and other flotsam above the high tide mark.
Where are the other echinoderms? Look for tube-feet in unlikely places. Such as under a red or green sea urchin or under a dark red sea cucumber. Sea cucumbers are easier to pick up than sea urchins, and their tube-feet are obvious. There are big red sea cucumbers and small white ones out in the open, and red ones that live under rocks with only their feathery feeding plumes showing. Quite different in appearance and behavior, but all belong to the sea cucumber family. If you also discover that both the sea urchin and the sea cucumber have five segments, like the sea star, then you may be confident that you have discovered more members of this interesting family of invertebrates. Echinoderms are important to the health of Puget Sound because they spend their lives cleaning up organic debris. Sand dollars are also in this family, but are less likely to be found on rocky beaches.
Where waves and currents are strong, rocks provide an essential anchor. Various species invent unique ways to hold their places. Barnacles and rock scallops use a permanent water-proof cement to stake their claim. Mussels use an amazingly strong glue and many small, tough organic threads that can be replaced if broken. Slow moving limpets, snails, chitons and abalone (yes we have abalone here) rely on a strong foot for suction to hold them in place.
Other shellfish abound. Cockles, scallops and various clams are found in sandy areas between the rocks. Surprisingly, fossils of some of these shellfish may be found in the nearby sandstone cliffs. There is nothing like the thrill of cracking a rock with a hammer and chisel and finding a perfect scallop shell inside! Grey, rounded fossil nodules are common. Many nodules are formed around a piece of organic material: a leaf, a crab claw, a crinoid stem, or a shell. As the soft organic material decomposes in the mud it gives off chemicals that harden the mud around it, eventually forming the rock nodule.
Fossil Crab in Natural Rock Nodule – Photo by Lyon McCandless
Many beach rocks have interesting stories to tell. Look for a fist-sized dark gray or black rock with white spots. You may be able to see wood grain or tree rings on the end, indicating that it is probably a piece of petrified wood. The white spots are actually the burrows of Toredo worms, now filled with a white mineral. You can be sure that this rock has had some interesting adventures.
It was once part of a living tree growing on dry land, breathing air and drinking fresh water. The fact that the rock exhibits wood-like grain and tree rings indicates that it was once a part of a deciduous tree. (Probably of the Cenozoic Era rather than the older Paleozoic or Mesozoic Eras which were dominated by giant ferns.) Except for sub-tropical salt water mangroves, most deciduous trees depend on fresh water in the atmosphere and ground. The fossil’s closely spaced tree rings indicate relatively slow growth in a climate with seasonal changes and an atmospheric makeup similar to the current one. A warmer atmosphere with higher CO2 content would result in wider growth rings.
The tree probably grew quite close to the ocean because eventually a fairly large piece of it was submerged in salt water. It may have been transported by a land slide. It must have stayed in salt water less than 100 feet deep for at least six months to become so infested with boring Toredo worms. Toredos, sometimes called the bane of wooden ships, look like a worm, but are a type of mollusk that burrows into wood instead of sand. What would be a shell in other mollusks has moved to the end of the Toredo and changed into jaws that gnaw into the wood.
The tree eventually sank to the sea bottom where it joined clamshells and crabs that were slowly being covered with mud and sand. And as the years went by it was buried so deep that the surrounding sand and clay became cemented together in a form of sandstone. Hot, mineralized water replaced all the wood fibers with stone, and filled the worm holes with calcite crystals.
Fossilized Wood with Toredo Holes – Photo by Lyon McCandless
The creation of a stony fossil requires heat, water and pressure. A burial depth of 500 feet or more would heat the water that fills the small spaces in the rock and would dissolve many of the minerals present. Subsurface water moves slowly through the pores of even relatively dense rock due to crustal flexing and changing tidal pressures. The water first saturates the wood and then gradually breaks down the softer parts and replaces them with silicates in a process called ‘permineralization’. The worm burrows were probably filled quickly with the relatively soluble calcite, and later on the wood itself was slowly replaced with another mineral.
Finally the slow movements of the earth’s tectonic plates lifted the whole layer of sandstone thousands of feet. Now above sea level, the thick layers of sedimentary rock were exposed to the forces of rain and weather. And the seemingly solid rock cliffs continuously crumble, bringing rocks and fossils to light for the first time in thousands of years, reminding us that nature is change.
Fossil wood with worm holes may be found adjacent to the cliffs on the south side of the straits of Juan de Fuca. The relatively soft sandstone cliffs slough off and weather away leaving harder rocks on the beach. Several types of fossil clams and fossil crabs are found near the fossil wood both in the sandstone cliffs and on the beach. These support the assumption that the sandstone is the original matrix in which permineralization occurred.
Fossil rocks with rounded edges indicate abrasion by wave or alluvial action. Nearby very similar pieces of petrified wood may be more jagged, more wood-like in appearance. Some do not have worm holes. The jagged samples must have weathered from the cliffs recently, while the rounded rock has been tumbled by wave action. New material is coming out of the cliffs all the time, just waiting to be discovered by some inquisitive person.
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