- published: 03 Apr 2012
- views: 364
A waterfall is a place where water flows over a vertical drop in the course of a stream or river. Waterfalls also occur where meltwater drops over the edge of a tabular iceberg or ice shelf.
Waterfalls are commonly formed when a river is young. At these times the channel is often narrow and deep. When the river courses over resistant bedrock, erosion happens slowly, while downstream the erosion occurs more rapidly. As the watercourse increases its velocity at the edge of the waterfall, it plucks material from the riverbed. Whirlpools created in the turbulence as well as sand and stones carried by the watercourse increase the erosion capacity. This causes the waterfall to carve deeper into the bed and to recede upstream. Often over time, the waterfall will recede back to form a canyon or gorge downstream as it recedes upstream, and it will carve deeper into the ridge above it. The rate of retreat for a waterfall can be as high as one and half meters per year.
Often, the rock stratum just below the more resistant shelf will be of a softer type, meaning that undercutting due to splashback will occur here to form a shallow cave-like formation known as a rock shelter under and behind the waterfall. Eventually, the outcropping, more resistant cap rock will collapse under pressure to add blocks of rock to the base of the waterfall. These blocks of rock are then broken down into smaller boulders by attrition as they collide with each other, and they also erode the base of the waterfall by abrasion, creating a deep plunge pool or gorge.
A drop zone (DZ) is a place where parachutists or parachuted supplies land. It can be an area targeted for landing by paratroopers, or a base from which recreational parachutists and skydivers take off in aircraft and land under parachutes. In the latter case, it is often beside a small airport, frequently sharing the facility with other general aviation.
At recreational drop zones, an area is generally set side for parachute landings. Personnel at the site may include a drop zone operator or owner (DZO), manifestors (who maintain the flight manifest documents defining who flies and when), pilots, instructors or coaches, camera operators, parachute packers and riggers, and other general staff.
Drop may refer to:
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Anti-aircraft flak lights up the evening sky
Enemy radar spotted our chopper's arrival
Rocket propelled grenade takes out one of four
Cast aside fear and tighten the grip on your M-16
Hueys stationary firing missiles and gattling guns
Cover our asses as we descend into battle
The choppers leave us behind / Hostile enemy lines
We must destroy their installations / Failure is not an option
Into the Drop Zone! Into the Drop Zone!
Our mission perfectly thought and mapped out
Ready thermal imaging and mine detection
Cannon fire ceases as we cut the enemy down
Mortars and grenade launchers utterly precise
They pushed our leaders to the brink of war
We warned you many times, "Don't fuck with the U.S.!"
The choppers leave us behind / Hostile enemy lines
We must destroy their installations / Failure is not an option
Into the Drop Zone! Into the Drop Zone!
The battle smoke begins searing the eyes, oh the pain
Corpses of our enemies lie smoldering about
I bleed from the lead I caught on that last hill
My blood-stained uniform a tribute to victory
The F-16's finish sweeping up the last enemies
We return home to our friends and families
The choppers leave us behind / Hostile enemy lines
We must destroy their installations / Failure is not an option
Into the Drop Zone! Into the Drop Zone!