Very quickly, the sand sinks to the bottom and the water floats to the top. This is where the salt comes in. When there’s enough salt present, as soon as the clay particles liquefy, electrical charges make them begin to stick together to form bigger particles and these also settle with the sand. Quicksand is a mixture which looks like solid, but behaves more like a liquid.

　　Despite its murderous reputation, quicksand does not such people under and swallow them, although it can hold a person in firm grip. The human body is more buoyant(有浮力) in quicksand than in water, and sooner or later anyone trapped in it will float.

　　Unlike most liquids, quicksand’s viscosity, or “runniness” can suddenly change if it comes under pressure, for example under a human foot. The surface gives way and the victim quickly sinks in up to the knees, surrounded by an area of dirty things that turns semi-solid around its victim. Escaping from the quicksand’s grip(紧握) requires a large amount of force. Without something solid to pull at, people often find they are stuck fast. Pulling at one leg simply makes the other one sink further.

　　So how do you escape from quicksand’s control? Stay still and call for help. Staying still stops you sinking any further, until--with luck--help arrives on the scene. If no one appears and you need to draw yourself out, gently lie down on your back until your body is floating on the sand. Next, roll over onto your stomach and pull yourself forwards with your hands, so that you gradually “swim” towards firmer ground. It is a slow and dirty business, but it works.

【决胜高考 2016高考英语黄金30题：专题06 考前必做难题30题（学生版）】相关文章：

★ 湖南省长沙县实验中学2016届高三英语二轮复习书面表达复习重点话题指导专题06 记叙概括话题指导（教师版）

★ 湖南省长沙县实验中学2016届高三英语二轮复习书面表达复习重点话题指导专题13 社会发展类话题指导（学生版）

★ 2014届高考英语一轮复习选修6参考答案（外研版）

★ 湖南省长沙县实验中学2016届高三英语二轮复习书面表达复习重点话题指导专题02 报道评论话题指导（学生版）

★ 湖南省长沙县实验中学2016届高三英语二轮复习书面表达复习重点话题指导专题20 校园学习话题指导（学生版）

★ 湖南省长沙县实验中学2016届高三英语二轮复习书面表达复习重点话题指导专题11 青少年成长话题指导（学生版）

★ 2014届高考英语一轮复习必修3参考答案（外研版）

★ 湖南省长沙县实验中学2016届高三英语二轮复习书面表达复习重点话题指导专题01 写作技巧（学生版）

★ 2017年高考英语二轮复习精品资料：专题16 书面表达（教学案）（教师版）

★ 湖南省长沙县实验中学2016届高三英语二轮复习书面表达复习重点话题指导专题03 辩论对比话题指导（学生版）