​A cave is a hollow place in the ground, specifically a natural underground space large enough for a human to enter. Caves are formed by the dissolution of limestone. Rainwater picks up carbon dioxide from the air and as it percolates through the soil, which turns into a weak acid. This slowly dissolves out the limestone along the joints, bedding planes and fractures, some of which become enlarged enough to form caves.

Karst, a type of landscape made of limestone, dolomite, and gypsum rocks that slowly dissolve in the presence of water with a slightly acidic tinge. ... The acidic water percolates down into the Earth through cracks and fractures and creates a network of passages like an underground plumbing system.

A Cavern is a specific type of cave, naturally formed in soluble rock with the ability to grow speleothems.

Speleothems ( /ˈspiːliːəθɛm/; Ancient Greek: "cave deposit"), commonly known as cave formations , are secondary mineral deposits formed in a cave. Speleothems typically form in limestone or dolostone solutional caves.

Stalactites hang from the ceiling; 

Stalagmites rise from the ground.

Cave Popcorn can form by precipitation. Water seeping through limestone walls or splashing onto them leaves deposits when CO2 loss causes its minerals to precipitate. When formed in this way the resultant nodules have the characteristics of small balls of flowstone.

A Soda Straw (or simply straw) is a speleothem in the form of a hollow mineral cylindrical tube. They are also known as tubular stalactites. Soda straws grow in places where water leaches slowly through cracks in rock, such as on the roofs of caves.

Pillars are a stalactite and a stalagmite grown together. ... It is rather common that stalactites and stalagmites meet and join. But as they grow very slowly it takes hundred thousands of years. After they meet they are called a pillar or Column. Sometimes the term Stalagnate is used.

Draperies. Among the most beautiful of cave formations, draperies are deposited from calcite-rich solutions flowing along an overhung surface. Surface tension allows these solutions to cling to a wall or sloping ceiling as they stream slowly downward.  Sometimes the term Curtains is used.

A Cave Pearl is a small, usually spherical, speleothem (cave formation) found in limestone caves. Cave pearls are formed by a concretion of calcium salts that form concentric layers around a nucleus.

Crystals  When magma underneath the mountain cooled and the temperature dropped below 58 degrees Celsius, the anhydrite began to dissolve. The anhydrite slowly enriched the waters with sulfate and calcium molecules, which for millions of years have been deposited in the caves in the form of huge selenite gypsum crystals.

Rose Quartz is a translucent pink to rose-red variety of quartz.  Among gemstones, rose quartz is considered a semiprecious stone that may be used in jewelry. Rose quartz stones that are nearly transparent are sometimes cut to make flat surfaces called facets, to better reflect light.  Rose quartz and other stones and crystals are formed when magma is pushed towards the earth’s crust and combines with different minerals along the way.  When this magma cools down, the different elements and minerals are bonded together to form a quartz crystal.

 Limestone is a sedimentary rock, composed mainly of skeletal fragments of marine organisms such as coral, forams and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3).  About 10% of sedimentary rocks are limestones. The solubility of limestone in water and weak acid solutions leads to karst landscapes, in which water erodes the limestone over thousands to millions of years. Most cave systems are through limestone bedrock.

The Iapetus Ocean was an ocean that existed in the late Neoproterozoic and early Paleozoic eras of the geologic timescale (between 600 and 400 million years ago). Because the Iapetus Ocean was positioned between continental masses that would at a much later time roughly form the opposite shores of the Atlantic Ocean, it can be seen as a sort of precursor of the Atlantic. The Iapetus Ocean was therefore named for the titan Iapetus, who in Greek mythology was the father of Atlas, after whom the Atlantic Ocean was named.  As this ocean spread over the land, it left behind thick deposits of sediments that hardened into layered sedimentary rocks. The youngest rocks in Shenandoah are river, lagoon, and beach deposits left behind by the early stages of the Iapetus. In the valleys and ridges to the west, thick sequences of limestone and other marine rocks preserve evidence for the rest of this underwater period.The ancient Grenville rocks, the lava flows, and the sediments represent the three main geologic units found within Shenandoah. All of these events occurred over 400 million years ago and the Appalachian Mountains had yet to appear on the scene! The Appalacian Mountains formed when the tectonic plates originally active during Grenville times reversed themselves and began to collide once more. This great collision between Europe and North Africa on one side and North America on the other closed the Iapetus Ocean and created a massive new mountain range as the thick layers of sediment that once lay miles below water were now thrust up into new summits. These were the Appalachian Mountains. At their peak around 350-300 million years ago, they were likely as large and dramatic as the Himalayas.

The Geological Formation of Shenandoah National Park began 1 billion years ago. Molten magma, miles beneath the earth's surface, slowly solidified to become the "basement rock," or core, of what we know today as the Blue Ridge Mountains.

Between 1.2 and 1.0 billion years ago, ancient collisions of tectonic plates raised a great mountain range, named Grenville by geologists. This process, very similar to the forces creating the Himalayas today, produced incredible heat and pressure that melted and deformed the rocks deep in the mountains’ core. These highly metamorphosed rocks are preserved within Shenandoah today and provide geologists a way to date the timing of these events. 

Shenandoah National Park straddles the Blue Ridge, a unique line of mountains forming the easternmost rampart of the great Appalachian Range. The story of Shenandoah’s mountains is the story of two mountain ranges, spanning over one billion years of earth’s history.

When pressures from these colisions eased, the peaks stopped rising, and erosion took over. For hundreds of millions of years, the once-lofty Grenville range slowly wore away, until it was no more than a landscape of rolling hills and occasional higher points, similar to the Virginia Piedmont found east of Shenandoah today. Evidence of this past terrain can still be seen in the shape of contacts between the old Grenville rocks and the younger rocks above. During this period primitive life was just beginning to flourish in oceans. 

Around 570 million years ago this stable scene ended violently as the underlying tectonic plates began to move apart. Vast quantities of lava rose through a developing system of rifts, erupting onto the surface along rift zones that stretched for thousands of miles along what is now eastern North America. For several million years, these lava flows filled in valleys and lapped against hillsides, until finally the rift between the plates grew so wide that water began to fill it, and a new ocean was born. 

Virginia is on the eastern edge of the North American continent - but we are not on the eastern edge of the North American tectonic plate. Virginia is closer to the middle of the tectonic plate than to the eastern edge. The eastern edge of the tectonic plate is the Mid-Atlantic Ridge in the middle of the Atlantic Ocean. The western edge is the San Andreas fault on the California coast, leaving Virginia in the middle.

 The topography of Virginia was formed through a series of continental collisions that created vast mountain ranges in Virginia. The modern Blue Ridge and the "mountains" to the west are tiny, compared to the ancestral Appalachian Mountains created with Africa and North America collided 300 million years ago. The original Appalachian were located roughly where I-95 is located today, far east of the current Blue Ridge. Those original Appalachians may have been 20,000 feet high or higher.2

 The collisions that created tall mountain ranges in Virginia were followed by erosion that has etched away those mountains. The eroded sediments have created the flat Appalachian Plateau west of Virginia, and the flat Coastal Plain east of I-95. The shorelines of the Atlantic Ocean and Gulf Coast have changed as the mountains washed away and as sea level has changed.

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