Water flowing over Earths surface or underground causes erosion and deposition. Water flowing over a steeper slope moves faster and causes more erosion. How water transports particles depends on their size. When water slows down, it starts depositing sediment. This process starts with the largest particles first. Runoff erodes the land after a heavy rain. It picks up sediment. Runoff carries most of the sediment to bodies of water. Mountain streams erode narrow, V-shaped valleys and waterfalls. Erosion and deposition by slow-flowing rivers create broad floodplains and meanders. Deposition by streams and rivers may form alluvial fans and deltas. Floodwaters may deposit natural levees. Erosion and deposition by groundwater can form caves and sinkholes. Stalactites and stalagmites are mineral deposits. They build up in caves as water continues to drip.

Where do stalactites and stalagmites occur?

So what is gravity? A typical definition of gravity is that it is a force. It causes an attraction between two masses. According to this definition, anything that has mass exerts a force. Any object exerts gravity on other objects. It does not matter how small it is, it has gravity. The more matter an object has, the more gravity it has. Your pencil has a tiny bit of gravity, but far too little to notice. What about a planet? It would have a lot of gravity. An objects gravity exerts a pull on other objects. Friction only occurs between objects that are touching. Gravity can act between objects that are not touching. In fact, gravity can act over very long distances. Where else can you feel gravity?

Does size matter when it comes to gravity?

The Agencies Confer When they learned a second plane had struck the World Trade Center, nearly everyone in the White House told us, they immediately knew it was not an accident. The Secret Service initiated a number of security enhancements around the White House complex. The officials who issued these orders did not know that there were additional hijacked aircraft, or that one such aircraft was en route to Washington. These measures were precautionary steps taken because of the strikes in New York. The FAA and White House Teleconferences. The FAA, the White House, and the Defense Department each initiated a multiagency teleconference before 9:30. Because none of these teleconferences-at least before 10:00- included the right officials from both the FAA and Defense Department, none succeeded in meaningfully coordinating the military and FAA response to the hijackings. At about 9:20, security personnel at FAA headquarters set up a hijacking teleconference with several agencies, including the Defense Department. The NMCC officer who participated told us that the call was monitored only periodically because the information was sporadic, it was of little value, and there were other important tasks. The FAA manager of the teleconference also remembered that the military participated only briefly before the Pentagon was hit. Both individuals agreed that the teleconference played no role in coordinating a response to the attacks of 9/11. Acting Deputy Administrator Belger was frustrated to learn later in the morning that the military had not been on the call. At the White House, the video teleconference was conducted from the Situation Room by Richard Clarke, a special assistant to the president long involved in counterterrorism. Logs indicate that it began at 9:25 and included the CIA; the FBI; the departments of State, Justice, and Defense; the FAA; and the White House shelter. The FAA and CIA joined at 9:40. The first topic addressed in the White House video teleconference-at about 9:40-was the physical security of the President, the White House, and federal agencies. Immediately thereafter it was reported that a plane had hit the Pentagon. We found no evidence that video teleconference participants had any prior information that American 77 had been hijacked and was heading directly toward Washington.
When did the video teleconference in the situation room begin?